The term 'Canine Warning' is a phrase used to describe the warning signs that a dog may give when it is feeling threatened or aggressive. The crossword solutions for this term are ACHE (4 letters), SNARL (5 letters), and GRR (3 letters). ACHE is a dull, continuous pain, which can be a sign of discomfort in a dog. SNARL is a low, guttural growl that is often accompanied by bared teeth, which is a clear sign of aggression. Finally, GRR is a sound that is usually made with a deep breath, and is a warning that the dog may attack if provoked.