一口咬定

to arbitrarily assert / to allege / to stick to one's statement / to cling to one's view

one / single / a (article) / as soon as / entire; whole; all; throughout / "one" radical in Chinese characters (Kangxi radical 1) / also pr. [yao1] for greater clarity when spelling out numbers digit by digit

readily / flatly (deny, admit and so on) / a mouthful / a bite

mouth / classifier for things with mouths (people, domestic animals, cannons, wells etc) / classifier for bites or mouthfuls

to bite / to nip

variant of 咬[yao3]

to assert / to insist that

to set / to fix / to determine / to decide / to order