mate-bacilli Share definition Flag Another way of saying, 'very horny'. Read it in a fanfiction by Neko Izumi in AFF.net Dude1: Why are you late? Dude2: My partner got infected by the mate-bacilli. You know what I mean. mate-bacilli by Z~K January 6, 2009 0 0 Get merch Get the mate-bacilli mug. Buy Now — $32.95 See more merch