'Pinning' definitions:

Definition of 'pinning'

From: WordNet
noun
A mutual promise of a couple not to date anyone else; on college campuses it was once signaled by the giving of a fraternity pin

Definition of 'Pinning'

From: GCIDE
  • Pin \Pin\, v. t. [imp. & p. p. Pinned; p. pr. & vb. n. Pinning.] [See Pin, n.] To fasten with, or as with, a pin; to join; as, to pin a garment; to pin boards together. "As if she would pin her to her heart." --Shak. [1913 Webster]
  • To pin one's faith upon, to depend upon; to trust to. [1913 Webster]