ag·ate 
(ăgĭt)
(ăgĭt)n.
1. A fine-grained, fibrous variety of chalcedony with colored bands or irregular clouding.
2. A playing marble made of agate or a glass imitation of it; an aggie.
3. A tool with agate parts, such as a burnisher tipped with agate.
4. Printing A type size, about 5 1/2 points.
[Middle English achate, agaten, from Old French acate, agate, alteration (influenced by Greek agathē, good) of Latin achātēs, from Greek akhātēs.]