The Collaborative International Dictionary of English v.0.48:

Somnolent \Som"no*lent\, a. [F. somnolent, L. somnolentus, from
   somnus sleep, akin to Gr. ?, Skr. svapna sleep, dream, svap
   to sleep, Icel. sofa, AS. swefn sleep. Cf. Hypnotic,
   Somnambulism, Soporific.]
   Sleepy; drowsy; inclined to sleep. -- Som"no*lent*ly, adv.
   [1913 Webster]

         He had no eye for such phenomena, because he had a
         somnolent want of interest in them.      --De Quincey.
   [1913 Webster]

WordNet (r) 3.0 (2006):

somnolently
    adv 1: in a drowsy manner; "`Time to get up,' she said drowsily"
           [syn: drowsily, somnolently]