v. 1a. To take the weight of; weigh. The man at the airport counter weighed in our bags and took our plane tickets. A doctor weighed in the wrestlers. 1b. To have yourself or something that you own weighed. Often used with "at". I weighed in at 100 pounds on the scale today. We took our bags to the airport counter to weigh in. 1c. To have yourself weighed as a boxer or wrestler by a doctor before a match. Often used with "at". The champion didn't want to weigh in at more than 160 pounds. 2. slang To join or interfere in a fight, argument, or discussion. We told Jack that if we wanted him to weigh in with his opinion we would ask him.
Compare: TAKE PART.