The Collaborative International Dictionary of English v.0.48:

Poplar \Pop"lar\, n. [OE. popler, OF. poplier, F. peuplier, fr.
   L. populus poplar.] (Bot.)
   1. Any tree of the genus Populus; also, the timber, which
      is soft, and capable of many uses.
      [1913 Webster]

   Note: The aspen poplar is Populus tremula and Populus
         tremuloides; Balsam poplar is Populus balsamifera;
         Lombardy poplar (Populus dilatata) is a tall, spiry
         tree; white poplar is Populus alba.
         [1913 Webster]

   2. The timber of the tulip tree; -- called also white
      poplar. [U.S.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

poplar
    n 1: soft light-colored non-durable wood of the poplar
    2: any of numerous trees of north temperate regions having light
       soft wood and flowers borne in catkins [syn: poplar,
       poplar tree]

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

Poplar

   Morris, 1978.  A blend of LISP with SNOBOL4 pattern matching
   and APL-like postfix syntax.  Implicit iteration over lists,
   sorting primitive.  "Experience with an Applicative
   String-Processing Language", J.H. Morris et al, 7th POPL, ACM
   1980, pp.32-46.