As nouns the difference between terms and underhead
is that terms is while underhead is (obsolete) a blockhead, or stupid person; a dunderhead.
As an adjective underhead is
(engineering) beneath the head of a mechanical component.
terms
English
Noun
(head)
Statistics
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underhead
English
Noun
(
en noun)
(obsolete) A blockhead, or stupid person; a dunderhead.
-
Adjective
(
-)
(engineering) Beneath the head of a mechanical component.
(
Webster 1913)