- any of three derivatives of ammonia in which one or all of the hydrogen atoms are replaced by methyl groups, especially a gas, CH5N, with an ammonialike odor, the simplest alkyl derivative of ammonia and, like the latter, forming a series of salts.
- a colourless flammable water-soluble gas, used in the manufacture of herbicides, dyes, and drugs. Formula: CH 3 NH 2
