adverb
any; at all; in the least; ever
Used in negative or conditional contexts to emphasize that something is not the case even to the slightest degree. Often paired with ない, なければ, or ても.
いやしくもそんなことは考えていない。
I haven't thought about such a thing at all.
いやしくも彼が嘘をつくはず
He would never lie, not in the least.