Definition of "Past" :

noun: a verb tense that expresses actions or states in the past

noun: the time that has elapsed

"Forget the past."

noun: a earlier period in someone's life (especially one that they have reason to keep secret)

"Reporters dug into the candidate's past."

adjective: of a person who has held and relinquished a position or office

adjective: earlier than the present time; no longer current

"Time past."

adverb: so as to pass a given point

"Every hour a train goes past."