The Collaborative International Dictionary of English v.0.48:

Lacunal \La*cu"nal\ (l[.a]*k[=u]"nal), Lacunar \La*cu"nar\
   (l[.a]*k[=u]"n[~e]r), a.
   Pertaining to, or having, lacun[ae]; as, a lacunar
   circulation.
   [1913 Webster]