咋 (zǎ) is a colloquial bound form (b.f.) used in Northern Mandarin to mean 'how' or 'why'. It appears in compounds like 咋样 ('how'), 咋办 ('what to do'), and 咋回事 ('what's happening'). The source gloss 'bite' is incorrect for this reading — that meaning belongs to the rare zé reading of the same character.