look up any word, like slope:
 
1.
(proposed definition)

Two areas underlap when there is a gap between them - rather than just touching.
When hanging wallpaper, you should arrange the sheets so that they neither overlap nor underlap.
by Ed Avis June 21, 2003
 
2.
to support from below; having strengths that work together without conflict
His personality underlapped hers and strengthened their team.
by Dennis P Ryan January 24, 2009
 
3.
The opposite of overlap, which technically means to skip or miss a part of something.
My fucking retarded teacher underlapped the design project, so we couldn't get it all.
by EC April 23, 2003