to put down or drop something heavy without caring where it goes, or to get rid of something or someone no longer wanted: The ship was accused of dumping ...
1 dump something on somebody to unfairly give someone an unwanted job, duty, or problem to deal with Don't just dump the extra work on me. ; 2 American English ...
The meaning of DROP/DUMP (SOMETHING) IN/INTO/ON SOMEONE'S LAP is to give (something) to someone suddenly even though he or she did not want it or expect it.