Meaning ‘down’, ‘off’, or ‘away from’, but sometimes used as an intensive prefix.

debacle
debar
debase
debate
debeak
debrief
debug
debunk
decaf
decamp
decant
decay
declaim
decease
deceit
decline
decode
decompose
deduce
deduct
deface
defang
default
defeat
defect
defend
defer
deficit
defile
deflate
deflect
defog
deform
defraud
defrock
defrost
defunct
defund
defuse
deject
delay
delete
delimit
delude
demean
dement
demob
demote
demur
denude
deny
depart
depict
depilatory
deport
depose
derail
deride
derive
desert (v)
desex
desist
detain
detach
detect
deter
detox