1. To become more muscular; to increase the size and strength of one's muscles. The coach said I would need to seriously muscle up during the off season if I wanted to make varsity next year. There's really no point muscling up if you aren't building up your aerobic fitness as well.
2. To cause an animal to have larger, stronger muscles. In this usage, a noun or pronoun can be used between "muscle" and "up." The breeder suggested a diet I could try to help muscle up the young colt. He wanted to muscle the guard dogs up so they would be more intimidating.
3. To lift someone or something up (something or some place) using only brute physical strength. In this usage, a noun or pronoun can be used between "muscle" and "up." You're going to seriously hurt yourself if you try to just muscle the furniture up the stairs like that. The man had been knocked unconscious, so the firefighter had to muscle him up onto her shoulders and carry him out of the building.
4. To control, dominate, or push around someone with great physical strength. In this usage, a noun or pronoun can be used between "muscle" and "up." They have a lot of big guys on the team, so they're going to try to muscle us up for the whole match. The bouncer started muscling me up after I tried to push my way through the club.
5. Of a country, to increase the size or presence of one's military forces. There have been concerns that their neighbors to the south have begun muscling up in anticipation of a global conflict. His security advisor suggested they muscle up north to prevent any further outbreaks of violence.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.