A lapse is a temporary slip, failure or break in continuity. Eating a second helping of cake when you're otherwise doing well on your diet is a lapse. Eating the whole cake in one sitting is a serious lapse in judgment.

First used to imply a “slip of the memory,” the noun lapse evolved in the sixteenth century from the Latin lapsus, meaning “a slipping and falling, falling into error.” The connotation of “a moral slip” developed later, and the verb form came into existence even later than that. Behaving badly one day when you're usually on your best behavior is a lapse; Behaving badly again after a short stint being well-mannered means you're lapsing back into nasty old habits.

Primary Meanings of lapse

drop to a lower level, as in one's morals or standards
a failure to maintain a higher state
end, at least for a long time
Full Definitions of lapse

v drop to a lower level, as in one's morals or standards

Type of:
drop away, drop off, fall away, slip
get worse

v go back to bad behavior

fall back, recidivate, regress, relapse, retrogress
Type of:
regress, retrovert, return, revert, turn back
go back to a previous state

v pass into a specified state or condition

pass, sink
Type of:
go or proceed from one point to another

v let slip

“He lapsed his membership”
Type of:
forego, forfeit, forgo, give up, throw overboard, waive
lose ( or lose the right to ( by some error, offense, or crime

v pass by

elapse, glide by, go along, go by, pass, slide by, slip away, slip by
fell, fly, vanish
pass away rapidly
Type of:
advance, go on, march on, move on, pass on, progress
move forward, also in the metaphorical sense

n a failure to maintain a higher state

backsliding, lapsing, relapse, relapsing, reversion, reverting
habitual relapse into crime
Type of:
an act that fails

n a mistake resulting from inattention

Type of:
error, fault, mistake
a wrong action attributable to bad judgment or ignorance or inattention

n a break or intermission in the occurrence of something

“a lapse of three weeks between letters”
Type of:
break, intermission, interruption, pause, suspension
a time interval during which there is a temporary cessation of something

v end, at least for a long time

“The correspondence lapsed
Type of:
cease, end, finish, stop, terminate
have an end, in a temporal, spatial, or quantitative sense; either spatial or metaphorical