tier 1 (tîr) n. 1. One of a series of rows placed one above another: a stadium with four tiers of seats. 2. A rank or class. tr. & intr.v. tiered, tier·ing, tiers To arrange (something) into or rise in tiers: tier a wedding cake; balconies that tier upward. [Middle English tire, row, rank, from Old French, from tirer, to draw out; see tirade.] ti·er ...