The Collaborative International Dictionary of English v.0.48:

Signal \Sig"nal\, v. t. [imp. & p. p. Signaled or Signalled;
   p. pr. & vb. n. Signaling or Signalling.]
   1. To communicate by signals; as, to signal orders.
      [1913 Webster]

   2. To notify by a signals; to make a signal or signals to;
      as, to signal a fleet to anchor. --M. Arnold.
      [1913 Webster]