Goes after definition- barks, pulls her leash, may bite at her leash, yodels, whines, etc
When Izzy goes after cats that are bigger than her I just grin and pull her back
When Izzy goes after any dog in existence, including, but not limited to; pitbulls, dobermans, rottwielers, bichon frise, rolling backpacks (apparently she thinks it's someone walking a "rolling dog") I pull her back and "ah ah!" her sternly
When Izzy goes after crows and herons I shake my head and tell her she can't fly
When Izzy starts growling and looking at the sky and I realize she's going after a helicopter! I post about it.