The definition used by the most patriotic humans on God's green Earth. NSOS can refer to any human both foreign and domestic that has a problem with having their God given rights stripped from them. However, is most recognized in the U.S.A. NSOS is derived from the "Don't tread on me" Gadsden flag: a yellow colored flag with a snake in the center- clearly meaning there are consequences when attempting to overtake or overthrow another human being, entity, company, or alike.
See: Claymore Roomba
See: Fuck around and find out
Scumbag 1- "Hey, let's go rob that fool's house.
Scumbag 2-"I wouldn't do that. There's a No Step On Snek flag hanging from his roof."
Scumbag 1- "It's a kid-drawing of a poorly drawn snake and grass. I'm going without you."
*Scumbag 1 has left the chat and reduced to pink mist due to being claymore roomba'd*
Scumbag 2- "Guess he fucked around and found out."