SIMCL is an internet acronym for Sitting In My Chair Laughing. A variant on the acronym "ROFL". SIMCL has been hailed as the more realistic description of what someone is actually doing when they use the term ROFL, that is, they are most likely not rolling on the floor and typing at the same time but sitting in their chair and laughing.
Michael: If I was king where do you think I should keep my armies?
John: In your sleevies.
Michael: simcl.
John: In your sleevies.
Michael: simcl.
by AMNotAlone August 11, 2010