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sow one’s wild oats

Meaning: indulge in youthful vices or excesses; behave wildly while young, especially having many sexual partners

предаваться грехам/утехам/забавам юности;
вести разгульную жизнь;
вести распущенный образ жизни
беситься, пока молодой

Bob was out sowing his wild oats last night. — Боб вчера где-то шатался, распутничал.

You're too old to be sowing your wild oats. — Тебе уж распутничать не по возрасту.

He'd spent his twenties sowing his wild oats but felt that it was time to settle down. — Он во всю предавался грехам юности в двадцать лет, но понял, что пришло время остепениться.

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The wild oat looks like the cultivated one but is actually merely a tall grass: to spend time and energy sowing it is therefore unprofitable. The expression sometimes implies sexual activity, probably as a result of the (implied) obsolete sense of 'seed' (semen).