The Collaborative International Dictionary of English v.0.48:

Lair \Lair\ (l[^a]r), n. [OE. leir, AS. leger; akin to D. leger,
   G. lager couch, lair, OHG. legar, Goth. ligrs, and to E. lie.
   See Lie to be prostrate, and cf. Layer, Leaguer.]
   [1913 Webster]
   1. A place in which to lie or rest; especially, the bed or
      couch of a wild beast.
      [1913 Webster]

   2. A burying place. [Scot.] --Jamieson.
      [1913 Webster]

   3. A pasture; sometimes, food. [Obs.] --Spenser.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lair
    n 1: the habitation of wild animals [syn: lair, den]