Definition for Tagma
From Biology Forums Dictionary
In biology a tagma is a specialized grouping of multiple segments or metameres into a coherently functional morphological unit. Familiar examples are the head, the thorax, and the abdomen of insects. The metameres within a tagma may be either fused (such as in the head of an insect or a mammal) or so jointed as to be independently moveable (such as in the abdomen of most insects).