1. slang A shortening of "session" (reflective of its pronunciation), referring to an extended period of time spent doing a specific activity, especially in a group. Typically used with a modifier specifying the activity. We're having a study sesh at Rachel's house, Mom! Be back in a few hours! Hey man, how about coming over to my house for a video game sesh later on? I'll be able to get a good amount of writing done if I have another sesh like last night.

2. A session of drug use, especially marijuana, especially in a group. Yo, sesh at my place later? I got a whole ounce!