The Collaborative International Dictionary of English v.0.48:

Tier \Ti"er\, n.
   One who, or that which, ties.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tier \Ti"er\, n. [See Tire a headdress.]
   A chold's apron covering the upper part of the body, and tied
   with tape or cord; a pinafore. [Written also tire.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tier \Tier\, n. [Perhaps fr. OF. tire, F. tire; probably of
   Teutonic origin; cf. OHG. ziar[imac] ornament, G. zier, AS.
   t[imac]r glory, ti['e]r row, rank. But cf. also F. tirer to
   draw, pull; of Teutonic origin. Cf. Attire, v. t., Tire a
   headdress, but also Tirade.]
   A row or rank, especially one of two or more rows placed one
   above, or higher than, another; as, a tier of seats in a
   theater.
   [1913 Webster]

   Tiers of a cable, the ranges of fakes, or windings, of a
      cable, laid one within another when coiled.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tier
    n 1: a relative position or degree of value in a graded group;
         "lumber of the highest grade" [syn: grade, level,
         tier]
    2: any one of two or more competitors who tie one another
    3: a worker who ties something [syn: tier, tier up]
    4: something that is used for tying; "the sail is fastened to
       the yard with tiers"
    5: one of two or more layers one atop another; "tier upon tier
       of huge casks"; "a three-tier wedding cake"