The Collaborative International Dictionary of English v.0.48:

Aspen \Asp"en\ ([a^]s"p[e^]n), Asp \Asp\ ([.a]sp), n. [AS.
   [ae]sp, [ae]ps; akin to OHG. aspa, Icel. ["o]sp, Dan. [ae]sp,
   Sw. asp, D. esp, G. espe, [aum]spe, aspe; cf. Lettish apsa,
   Lith. apuszis.] (Bot.)
   One of several species of poplar bearing this name,
   especially the Populus tremula, so called from the
   trembling of its leaves, which move with the slightest
   impulse of the air.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Aspen \Asp"en\ ([a^]s"p[e^]n), a.
   Of or pertaining to the aspen, or resembling it; made of
   aspen wood.
   [1913 Webster]

         Nor aspen leaves confess the gentlest breeze. --Gay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

aspen
    n 1: any of several trees of the genus Populus having leaves on
         flattened stalks so that they flutter in the lightest wind

The Free On-line Dictionary of Computing (19 January 2023):

ASPEN

    A toy language for teaching compiler
   construction.

   ["ASPEN Language Specifications", T.R. Wilcox, SIGPLAN Notices
   12(11):70-87, Nov 1977].

   (1994-11-30)