The Collaborative International Dictionary of English v.0.48:

Groin \Groin\, v. t. [imp. & p. p. Groined (groind); p. pr. &
   vb. n. Groining.] (Arch.)
   To fashion into groins; to build with groins.
   [1913 Webster]

         The hand that rounded Peter's dome,
         And groined the aisles of Christian Rome,
         Wrought in a sad sincerity.              --Emerson.
   [1913 Webster]