I've heard it differently from different MCs or MC-equivalents in the various games I've tried at cons. To pick one as an example, if I'm playing Apocalypse World, is this fine?
MC: So you were probably wondering when that 6- on the love letter was going to come due, Keeler? Well, it's right now. You're up top piloting the boat when the hatch to the bridge gets violently kicked open. It's Dremmer! And he's got a shotgun! And he says, "Hard to port, Keeler. Right. Fu[nn]ing. NOW!" What are you doing?
ME: Are we in danger if I let go of the wheel?
MC: Not for a little while. What are you planning?
ME: Okay, so I make like I'm gonna play along, and then let go of the wheel and dive for cover. I'm hoping I have enough time to get my gun out and make this a little less one-sided. That's acting under fire, surely.
Sometimes I've been told it's against the rules to say the name of the move I think I'm making like that.