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1.
beast infection comes from The commonly used term beast meaning that one looks tough, ripped, cut, has an intimidating presence,or that they are really good at something. Saying that someone has a beast infection is a slang or funny way to call some one or some thing a beast.
hat team must have a beast infection they win the championship every year.

dayum that dude has a severe beast infection
by hahhhhahha October 29, 2009
 
2.
To be inundated with an awesome aura of energy that infiltrates others around you akin to an aphrodisiac virus.
That guy has been lifting and dieting so much that his beast infection has turned critical
by ArtofAwesome October 09, 2013
 
3.
a male yeast infection
i didn't wash my jimmy for three weeks and got a mad beast infection
by turdburglar0 May 12, 2011