Green’s Dictionary of Slang

heavyweight n.

1. an important person with power and influence.

B.F. Taylor Summer-Savory xviii 146: He is a heavy-weight wherever he is [DA].
Century Mag. (N.Y.) 2764/3: Heavy-weight [...] A person of weight or importance; one of much influence [DA].
[US]H. Green Actors’ Boarding House (1906) 146: The music started; so did the dancing [...] Birdie, excited, caught up her skirts and joined the heavyweights.
[US]D. Hammett ‘This King Business’ Story Omnibus (1966) 121: Mentally he wasn’t a heavyweight. His revolution was crude stuff.
[US]H.S. Thompson Hell’s Angels (1967) 43: A bad hack job that wouldn’t have raised a ripple had it appeared in most American newspapers ... but the Times is a heavyweight.
[UK]G.F. Newman You Flash Bastard 245: Sneed didn’t say anything. He wasn’t about to be drawn into an argument between two heavyweights, especially not when one was his current boss.
[US]E. Folb Runnin’ Down Some Lines xxi: They self-educated [...] Ain’t no organization, but they heavyweights.
[US]D. Burke Street Talk 2 171: When he tells the employees to do something, they listen. He’s a real heavyweight.
[Aus]M.B. ‘Chopper’ Read Chopper 4 151: I’m one crook who has shaken hands with more heavyweights in all walks of life than most uppity NSW lawyers will get to meet in a lifetime.

2. (US Und.) a violent criminal.

[US]Jackson & Hellyer Vocab. Criminal Sl. 43: heavyweight [...] A desperate thief; a person capable of delivering a dangerous attack in the event of personal encounter; a yegg; a burglar.
[US]‘Blackie’ Audett Rap Sheet 166: With all them heavyweights of the old days thinning out, Johnny Chase was getting moved up on the firing line by the feds.

3. (US) a fat person, esp. a fat woman.

[US]G. Underwood ‘Razorback Sl.’ in AS L 1/2 61: heavyweight n Overweight person, especially a female.

4. (US gay) the possessor of a larger-than-average penis.

[US]B. Rodgers Queens’ Vernacular.

5. (US campus) a heavy drinker.

[US]Eble Campus Sl. Apr. 3: heavyweight – person who can drink a lot.