Combination of "Heisenberg Uncertainty Principle" and "bro." A bro cannot be both a bro and a boyfriend/husband at the same time. If he's with other bros, he acts one way: usually vulgar and rude. If he's with his girlfriend/wife, he acts another way: sweet and charming. He can never act exactly like a bro if he is with both bros and his girlfriend or wife.
One often observes the Heisenbro Uncertainty Principle at weddings.
by Ae5Ea8 March 2, 2015
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