pin down

(verb) define clearly. Synonyms: pin down, peg down, nail down, narrow down, narrow, specify. Example: "I cannot narrow down the rules for this game."

(verb) place in a confining or embarrassing position. Synonyms: trap, pin down. Example: "He was trapped in a difficult situation."

(verb) attach with or as if with a pin. Synonyms: pin down, pin up. Example: "Pin up a picture."