n. 1.an authoritative direction or instruction to do something 2.a military unit or region under the control of a single officer 3.the power or authority to command 4.availability for use 5.a position of highest authority 6.great skillfulness and knowledge of some subject or activity 7.(computer science) a line of code written as part of a computer program command v. 1.be in command of 2.make someone do something 3.demand as one's due 4.look down on 5.exercise authoritative control or power over