Unawares
Synonyms: By surprise, without warning, abruptly, off-guard, red-handed, in flagrante delicto, napping, on the hop, unwittingly, without noticing, unintentionally, accidentally, by mistake, unexpectedly, suddenly, unprepared, cold, in the act, with one's trousers/pants down, in flagrante, unknowingly, unconsciously, in all innocence, inadvertently, by accident, and mistakenly.
Example Sentences
The cat pounced on him unawares.
She arrived at the party unawares.
He caught her unawares while studying.
They walked into trouble unawares today.