used after a verb to indicate that an action cannot be completed or that there is no room for it, such as in 容纳不下 róng​nà​bù​xià

not less than; at least; often used to describe a quantity or amount that exceeds a certain level

to remain unchanged or unresolved; to be locked in a stalemate, such as in the phrases 僵持不下 jiāng​chí​bù​xià or 居高不下 jū​gāo​bù​xià

to be unable to conquer or seize a position, city, or stronghold