The Collaborative International Dictionary of English v.0.48:

Ringtail \Ring"tail`\, n.
   1. (Zool.) A bird having a distinct band of color across the
      tail, as the hen harrier.
      [1913 Webster]

   2. (Naut.) A light sail set abaft and beyong the leech of a
      boom-and-gaff sail; -- called also ringsail.
      [1913 Webster]

   Ringtail boom (Naut.), a spar which is rigged on a boom for
      setting a ringtail.
      [1913 Webster]