Give to someone suddenly or without warning. What is given may be desirable, as in I'm just going to drop the promotion in her lap this afternoon, or it may be burdensome, as in They simply dropped the employment problem in our laps. The former usage dates from the mid-1500s, the latter from the mid-1900s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.