Louse Share definition Flag A derogatory word, used for someone who is involved in idiocy or mishaps. Closely related to the word lousy but referring to self or others. "I just dropped the TV and broke it. I'm such a louse." "He is always so clumsy, what a louse." Louse by trko January 31, 2009 0 0 Get merch Get the Louse mug. Buy Now — $32.95 See more merch