What do contractions feel like?

Nurse Jo, very nice nurse who stayed and worked with us through out the wee hours of the AM, states contractions feel like the brain freeze sensation when you bite into cold ice cream. Except if one is having labor pains are in the back, the pain feel like it's shooting up your ass, although in reality there's nothing shooting up, rather it is a downward moving sensation since ultimately the baby is shooting on out downwards. Well at least that's what I'm hoping for :) Things you learn while sleeping on the cot in the labor room.