Wow, at some of you. Fucking idiots.
Yes, it's rape.
Sex is a choice or agreement between to people, like any contract. It has provisions. You violate the provisions, you're liable.
Let's break it down for some of you children.
If he/she says "stop" in the middle of sex and you keep going, it's rape. Duh.
If he/she says "sure, if you use a condom," then you were only given consent to sex on the provision that a condom is worn. If one is not worn, they are not consenting. JFC. If you keep going knowing full well you're breaking the agreement, knowing full well your partner would have told you to stop had they known what you were doing, It's rape. Not all rape is violent. Get over yourselves.