The Collaborative International Dictionary of English v.0.48:

Stagnate \Stag"nate\ (st[a^]g"n[=a]t), v. i. [imp. & p. p.
   Stagnated (-n[asl]*t[e^]d); p. pr. & vb. n. Stagnating.]
   [L. stagnatus, p. p. of stagnare to stagnate, make stagnant,
   from stagnum a piece of standing water. See Stank a pool,
   and cf. Stanch, v. t.]
   1. To cease to flow; to be motionless; as, blood stagnates in
      the veins of an animal; hence, to become impure or foul by
      want of motion; as, air stagnates in a close room.
      [1913 Webster]

   2. To cease to be brisk or active; to become dull or
      inactive; as, commerce stagnates; business stagnates.
      [1913 Webster]

            Ready-witted tenderness . . . never stagnates in
            vain lamentations while there is any room for hope.
                                                  --Sir W.
                                                  Scott.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Stagnate \Stag"nate\ (-n[asl]t), a.
   Stagnant. [Obs.] "A stagnate mass of vapors." --Young.
   [1913 Webster]

WordNet (r) 3.0 (2006):

stagnate
    v 1: stand still; "Industry will stagnate if we do not stimulate
         our economy"
    2: cause to stagnate; "There are marshes that stagnate the
       waters"
    3: cease to flow; stand without moving; "Stagnating waters";
       "blood stagnates in the capillaries"
    4: be idle; exist in a changeless situation; "The old man sat
       and stagnated on his porch"; "He slugged in bed all morning"
       [syn: idle, laze, slug, stagnate] [ant: work]