What does the PRESSURE of an epidural feel like?

I keep hearing girls talking about getting their epidurals and they all mention this immense pressure. Just curious what it feels like. Does it feel like you're being crushed or hit by a truck or something? I just don't really get what they felt. I'm about to have my baby within the next month and do plan on having the epi(please, no negative comments!) and I'm just curious about the sensation of it.