A contraction of the word something. Usually used in chat rooms or games. Can also be said out to save time while talking.
In a chatroom: Duh, tell me sumn I don't know.
While speaking: My boss told me to sumn and throw it away but idk
1. Temperatures below zero degrees
2. An original Mortal Kombat character
3. A Batman movie
1. Meteorologist John Smith says to expect subzero temperatures tomorrow
2. Subzero fatality!