It's often written in katakana: イク. If it's written like that, you know it's the sexual meaning.
In hentai, women often say イっちゃう when they're about to/in the middle of cumming (sometimes gay men do too), which sounds very feminine. The men usually just say イク or イキそう (this is gender neutral though!), when they say anything at all (they often don't).
I came: イっちゃった (feminine), イった (general).
Whether people actually say that in the bedroom, though, I couldn't tell you, lol. Hentai and reality are completely different beasts.
Be careful when using it, it's absolutely scandalous (as you can see by the other poster refusing to tell you).