shew, show, demonstrate, prove, establish - establish the validity of something, as by an example, explanation or experiment; "The experiment demonstrated the instability of the compound"; "The mathematician showed the validity of the conjecture"

blackguard, guy, jest at, laugh at, make fun, poke fun, ridicule, roast, rib - subject to laughter or ridicule; "The satirists ridiculed the plans for a new opera house"; "The students poked fun at the inexperienced teacher"; "His former students roasted the professor at his 60th birthday"

weaken - lessen the strength of; "The fever weakened his body"