Various Earth Mecha shown off to key members of the Sentinels. From left to right: a Destroid Defender, a Destroid Spartan, a Destroid Tomahawk, a Armored VF-1 Valkyrie, and an AJAX Fighter. (Robotech II: The Sentinels: The Invid Must Die!)
Mecha was the general term for any vehicle that has large-scale robotic or bioengineered limbs.
The Japanese usage of "mecha" differs from it's western usage. There "mecha" can mean anything mechanical from Petite Cola robotic vending machines to cars to the Macross.