プログレッシブ和英中辞典(第4版)の解説
ゆだん【油断】
油断する 〔不注意である〕be careless ((about))；〔警戒を怠る〕be off (one's) guard ((toward))
あの人はいつも油断がない
He is always on (his) guard.
油断なく仕事をしなさい
Don't be negligent [careless] in your work.／Be careful in your work.
消費者団体は便乗値上げはないかと油断なく見張っていた
Consumer groups were constantly on the lookout for cases of price gouging.
油断に乗じられてまんまとだまされた
Caught off guard, I fell for the trick completely.
油断していて不意をつかれた
I was caught napping.
あの男に油断するな
Don't take your eye(s) off that man.／Be careful of that man.
油断するとまた病気になりますよ
If you aren't careful, you'll get sick again.
油断しているすきに財布をすられた
I had my pocket picked 「in an unguarded moment [when I was off (my) guard].
油断も隙もない
東京は油断もすきもないところだ
You 「cannot be too careful [have to be constantly on your guard] in Tokyo.
油断大敵
Carelessness [Overconfidence] is our greatest enemy.（▼overconfidenceは自信過剰）