Something that is imminent is just about to happen: if you light a firecracker and then stick it down your pants, a very bad situation is imminent.
Imminent is from Latin imminere "to overhang," and to say that something is imminent is to say that it is hanging over you and about to fall, in a metaphorical way. If you take your mom’s car and drive it into the mailbox, getting grounded is imminent. You don’t want that hanging over your head!