Here in the US, playing keyboards typically refers to playing any one of the following:

Piano
Synthesizer
Arranger Keyboard
Electronic Piano

Interestingly enough, in Europe (except the UK), if you say you play keyboards, it specifically refers to playing an 'arranger' keyboard, not a synthesizer, piano, or even an electronic piano. I found this quite an interesting revelation, having learned this when speaking with Joost (Synthzone member Tostie), who lives in the Netherlands) on Skype today. I love Skype because it provides the opportunity to live voice & video chat (for free) with arranger keyboard friends from all around the world. Joost, it was a pleasure video-voice chatting with you today. - Scott