Real Dictionary

weigh in
phrasal verb: If someone weighs in at a particular weight, for example before competing in a sports competition, their weight is measured at that amount.
phrasal verb: If you weigh in on a plan, decision, or discussion, you add your advice or comments to it.

weigh-in
(of a boxer or wrestler) to be weighed before a bout
an official weighing in of a boxer, wrestler, jockey, etc., as before a contest
to be weighed by a medical examiner on the day of a bout
to weigh (a boxer, jockey, etc.) before or after a contest in order to verify declared weight
When there is a weigh-in on the day of a boxing match, each competitor is weighed to check their weight before the match.
noun: the act of checking a competitor's weight
noun: the act of checking a competitor's weight, as in boxing, horse racing, etc
noun: the act or an instance of weighing in