March hare

noun

a hare during its breeding season in March, noted for its wild and excitable behaviour (esp in the phrase mad as a March hare)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Examples from the Web for march hare

  • The Oracle and the over-production men will totally supplant the March-hare.

    Rural Rides|William Cobbett
  • He is mad as a March-hare himself, by all accounts; but everybody likes him.

    Perlycross|R. D. Blackmore