dastardly.adjective
characterized by underhandedness or treachery.(a dastardly attack) (a dastardly villain) 
dastardliness, dastard.nouns
mean; brutal

data.noun.plural
facts or figures from which conclusions can be inferred

DDT (dichlorodiphenyltrichloroethane).noun
a colorless contact insecticide, C₁₄H₉CL₅, (14 parts {molecules} carbon, 9 parts hydrogen, 5 parts chlorine), toxic to human beings and animals when swallowed, absorbed through the skin or breathed. It has been banned in the United States and Canada for most uses since 1972 

death house.noun
a place where prisoners await execution

debacle.noun
a sudden, disastrous collapse, downfall, or defeat; a rout; a total, often ludicrous failure; a violent flood

debauchery.noun.plural.debaucheries
extreme indulgence of one's appetite for sensual pleasures; selfish sensuality; orgies
debauch.transitive verb
corrupt; to lead astraymorally
debauch.noun
the act or a period of debauchery; an orgy
debauchment.noun
debaucher.noun
debauchedly.adverb
in a debauched manner 
debauchee.noun
a person who indulges in debauchery; a depraved person; debased
debauch, debauched, debauching, debauches.verbs
transitive verb use.to corrupt morally; to lead away from excellence or virtue; to reduce the value, quality, or excellence of; debase; corrupt
intransitive verb use.to indulge in dissipation

debris.noun
the scattered remains of something broken or destroyed; rubble or wreckage
Biology.–.the fragmented remains of dead or damaged cells or tissue

decay.noun
to fall into ruin (a civilization that had begun to decay)
transitive use.to cause to decay; the destruction or decomposition of organic matter as a result of bacterial or fungal action; rot
decayer.noun
decay.verb
decayed, decaying, decays.intransitive verbs
Biology.–.to break down into component parts; rot
Physics.–.to disintegrate or diminish by radioactive decay; an unstable nuclide changing its state; there is alpha, beta, gamma, and exponential decay
Electronics.–.to decrease gradually in magnitude

deception-noun
the use of deceit; the fact or state of being deceived; a ruse; a trick

deceive, deceived, deceiving, deceives.transitive verbs
to cause to believe what is not true (he was deceived into believing what the commonality of mankind had accepted); delude; mislead; beguile; betray
deceptive.adjective
tending to deceive; mislead
deceivable.adjective
deceiver-noun
deceivingly.adverb

deceptive.adjective
tending to deceive; misleading
deceptiveness.noun

deceitful.adjective
given to cheating or deceiving; deliberately misleading; deceptive; dishonest; beguiling
deceitfully-adverb
deceitfulness-noun

deceit.noun
the act or practice of deceiving; deception; a stratagem; a trick; the quality of being deceitful; falseness

decimate, decimated, decimating, decimates.transitive verb
to destroy or kill a large part of (a group); to select by lot and kill one in every ten of; to punish every tenth person (from decimus, tenth)
decimation-noun

decipher, deciphered, deciphering, deciphers.transitive verb
to read or interpret ambiguous, obscure, or illegible matter; solve; to convert from a code or cipher to plain text; decode
decipherable.adjective
decipherer, decipherment.noun

decorum.noun
whatever is suitable or proper; propriety and good taste in behavior; conducting one's life in a wise manner

dawdle, dawdled, dawdling, dawdles.verbs
intransitive use.to take more time than necessary (dawdled through breakfast); to move aimlessly or lackadaisically (dawdling on the way to work)
transitive use.to waste (time) by idling (dawdling the hours away)
dawdler.noun
dawdlingly.adverb

decree, decreed, decreeing, decrees.verbs
to order, decide, or appoint by decree
transitive verb use.to ordain, establish, or decide by decree
intransitive verb use.to issue a decree
decree, decreer.nouns
an official order; an authoritative order having the force of law
decreeable.adjective

decrepit.adjective
weakened, worn out, impaired, or broken down by old age, illness, or hard use; weak 
decrepitly.adverb

decry.transitive verb
to depreciate; to express strong disapproval of (decry the emphasis on sex); deprecate; disparage; belittle
decrier.noun

deduce, deduced, deducing, deduces.transitive verbs
to trace the course or derivation of; to conclude, to reach a conclusion by reasoning; to infer from a general principle by deductive reasoning
deducible.adjective

deduction.noun
in logic: the act or process of deducing; reasoning from a known principle to an unknown, from the general to the specific, or from a premise to a logical conclusion (opposed to induction); the drawing of a conclusion by reasoning; the process of reasoning in which a conclusion follows necessarily from the stated premises; inference by reasoning from the general to the specific; a conclusion reached by this process; subtraction

deductive.adjective
reasoning based on deduction
deductively.adverb
compare inductive

deem, deemed, deeming, deems.verbs
transitive verb senses.to regard as; consider (deemed the results conclusive); think; believe; to have as an opinion; to come to think or judge – consider (deemed it wise to go slow); judge 
intransitive verb senses.to have an opinion – believe; consider

dudhead.noun
a dull witted, sluggish or disappointingly ineffective or unsuccessful person

designate, designated, designating, designates.transitive verbs
to indicate or specify; point out; to give a name or title to; characterize; to select and set aside for a duty, an office, or a purpose; allocate; appoint
designate.adjective
appointed but not yet installed in office (the commissioner designate
designative or designatory.adjective
designator.noun

designation.noun
the act of designating; a marking or pointing out; a distinguishing name or title; name

diametrical also diametric.adjective
exactly opposite; contrary; of, relating to, or along a diameter
diametrically.adverb

dilly-dally, dilly-dallied, dilly-dallying, dilly-dallies.intransitive verbs
to waste time, especially in indecision; dawdle or vacillate
dilly-dallier.noun

debase, debased, debasing, debases.transitive verbs
to make lower in quality, character or dignity; degrade; adulterate; corrupt
debasement.noun
debaser.noun