unawares

adverb

1 a party of brigands caught them unawares:

by surprise, unexpectedly, without warning, suddenly, abruptly, unprepared, off-guard, cold;

red-handed, in the act, in flagrante delicto;

informal with one's trousers/pants down, napping, in flagrante;

British, informal on the hop.

▷antonyms prepared.

2 a shoal of young roach approached the pike unawares:

unknowingly, unwittingly, unconsciously, without noticing, in all innocence;

unintentionally, inadvertently, accidentally, by accident, by mistake, mistakenly.

▷antonyms knowingly; deliberately.

unawares Oxford Dictionary of English