The Collaborative International Dictionary of English v.0.48:

Stagnant \Stag"nant\ (-nant), a. [L. stagnans, -antis, p. pr. of
   stagnare. See Stagnate.]
   1. That stagnates; not flowing; not running in a current or
      steam; motionless; hence, impure or foul from want of
      motion; as, a stagnant lake or pond; stagnant blood in the
      veins.
      [1913 Webster]

   2. Not active or brisk; dull; as, business is stagnant.
      [1913 Webster]

            That gloomy slumber of the stagnant soul. --Johnson.
      [1913 Webster]

            For him a stagnant life was not worth living.
                                                  --Palfrey.
      [1913 Webster]

WordNet (r) 3.0 (2006):

stagnant
    adj 1: not circulating or flowing; "dead air"; "dead water";
           "stagnant water" [syn: dead(a), stagnant]
    2: not growing or changing; without force or vitality [syn:
       stagnant, moribund]