pinpoint

(noun) a very brief moment. Example: "They were strangers sharing a pinpoint of time together."

(noun) a very small spot. Synonyms: speck. Example: "The plane was just a speck in the sky."

(noun) the sharp point of a pin.

(verb) locate exactly. Synonyms: nail. Examples: "Can you pinpoint the position of the enemy?." "The chemists could not nail the identity of the chromosome."