The Collaborative International Dictionary of English v.0.48:

monopteral \mo*nop"ter*al\ (m[-o]*n[o^]p"t[~e]r*al), a. [Gr.
   mono`pteros with a row of pillars only; mo`nos alone, only +
   ptero`n feather, wing, also, a row of pillars: cf. F.
   monopt[`e]re.] (Arch.)
   Round and without a cella; consisting of a single ring of
   columns supporting a roof; -- said esp. of a temple.
   [1913 Webster]

WordNet (r) 3.0 (2006):

monopteral
    adj 1: having circular columniation