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adjective: earlier than the present time; no longer current
adverb: so as to pass a given point
"Every hour a train goes past."