[tier] n [MF tire rank, fr. OF--more at attire] (1569) 1 a: a row, rank, or layer of articles; esp: one of two or more rows, levels, or ranks arranged one above another b: a group of political or geographical divisions that form a row across the map "the southern ~ of states"
2: class, category
[2]tier vt (ca. 1889): to place or arrange in tiers ~ vi: to rise in tiers [3]ti.er n (1633): one that ties