What does the word mettlesome mean?

Usage examples for mettlesome

  1. Carleton was gazing fiercely at me as he came forward; and as his horse came opposite, pulled him up with a wrench on the bridle rein so violent that the mettlesome steed all but cast himself on his haunches. – Cedric, the Forester by Bernard Gay Marshall
  2. It describes a mettlesome horse. – An Introduction to Shakespeare by H. N. MacCracken F. E. Pierce W. H. Durham