Spherical is a related term of plump.
As adjectives the difference between spherical and plump
is that
spherical is (
label) shaped like a sphere while
plump is having a full and rounded shape; chubby, somewhat overweight.
As a verb plump is
to grow ; to swell out.
As an adverb plump is
directly; suddenly; perpendicularly.
As a noun plump is
(obsolete) a knot or cluster; a group; a crowd.