好不

adverb

so; what a; how (intensifying an adjective with exclamatory tone)

Generally interchangeable with just "好" (hǎo) before the adjective, both meaning 'very' in an affirmative sense (e.g., 好热闹 = 好不热闹 = very lively). The exception is with "容易" (róngyì, easy), where both "好容易" and "好不容易" mean 'not easy' or 'with great difficulty'. It often carries a stronger, more emotional emphasis than a simple "很" (hěn).