expression
(not) in the slightest; (not) at all
Slang expression used with a negative verb to mean 'not even a tiny bit'. Derived from ビタ一文 (bita ichimon), meaning 'not a single mon (old coin)'. Stronger and more emphatic than 全然.
See also: ビタ一文
あの映画、ビタイチ面白くなかった。
That movie wasn't interesting in the slightest.
彼の言うことはビタイチ信用できない。
I can't trust a single word he says.