chem /kɛm/noun 4adjective 1forms 1 noun[in the plural]4 •(informal) A chemical weapon. •Clipping of chemistry (“branch of natural science”), usually referring to the subject or the department.It boils down to science. Biology, chemistry and physics. I used to hate bio and chem. Now they fascinate me because I’ve realised they make up the world around us as well as us. — 2015 •(informal) A recreational drug.When you think ‘drugs’, you think Trainspotting. ‘Chems’ is easier off the tongue and, although explicit, it doesn't feel quite as bad. At least to us. — 2017 •(informal) Clipping of chemical. adjective1 •(informal) Clipping of chemical.chem plant; chem weapons formschems