Allide isn't a word you hear much. I don't think I'd have come across it myself if I didn't happen to be married to a handsome and extremely talented maritime photographer (that's me in Brownie points for a while!)
You know what collide means, I expect. Well, allide is like that, but only one of the objects is moving. Just as you can witness a collision when two moving objects strike each other, an allision is the action of a moving object hitting a stationary object.
Allision seems to be used almost exclusively in connection with ships. Sometimes one allides against another, more commonly a pier or mooring pontoon is involved.
This is Norwegian Epic. She recently allided with a pier in Puerto Rico. (And you thought I was making this up, didn't you?)