The Collaborative International Dictionary of English v.0.48:

Acerose \Ac"er*ose`\, a. [(a) L. acerosus chaffy, fr. acus, gen.
   aceris, chaff; (b) as if fr. L. acus needle: cf. F.
   ac['e]reux.] (Bot.)
   (a) Having the nature of chaff; chaffy.
   (b) Needle-shaped, having a sharp, rigid point, as the leaf
       of the pine.
       [1913 Webster]

WordNet (r) 3.0 (2006):

acerose
    adj 1: narrow and long and pointed; as pine leaves [syn:
           acerate, acerose, acicular, needle-shaped]