A conversational gambit is a opening used to start a conversation with someone you don't know. Often this is called, "chatting up" or maybe "hitting on" someone; but sometimes it's just wanting to talk.
Common conversational gambits are:
Conversational gambits are always completely safe and almost universally boring, but that's okay because you're supposed to pick up on an interesting thread of conversation and follow that.
Personally, I think it's better to start with the interesting threads and skip the conversational gambit altogether, but some people are skittish and will shy away from you if you start with, "Hi, I'm eric+. So, what color are your panties?"