As others have pointed out, Wikipedia gives the accepted definition, "a military service weapon that fires a full power rifle cartridge" and then they go on and blow it by including the M-16/AR-15.
5.56x45mm is NOT a full power cartridge. 7.62x39mm is NOT a full power cartridge. 30-06, 7.62x54R and 7.62x51mm ARE examples of full power rifle cartridges.
Here's a good essay on some issues they have in Afghanistan with the M16.