Today, you usually know who's calling before you answer. It may be appropriate to take a call if it's more important than the meeting. If you're in sales, a call from a major customer is probably more important than a meeting.
Sure, but not in the meeting. Excuse yourself, and explain it's an extremely important customer call that absolutely cannot wait.
And even if this is the case, you're still being rude... just with an excuse. The call may be more important to you, but the other people in the meeting? You're wasting their time.
If you've blocked out time for a meeting, don't take calls during that time. It's rude and unprofessional.
Note: This is for orgs that have effective meetings. If your meetings are generally unproductive, it may be a different story...