Within the context of handguns, "auto" implies semi-auto to me. If I happen to be talking about a Beretta 93R or a Glock 18, I'll qualify my terms.
I'm reminded of a scene from The Adventures of Tintin, The Black Island, where Tintin gets the jump on two bad guys and gets a pistol from one. He ties them up, and one remembers his pistol isn't loaded. They start yelling for help, so Tintin cold-cocks both of them unconscious, quipping "there's more than one way to use an automatic." Great lesson for the six year old Devonai.