midriff vs midsection

midriff and midsection both are nouns.

Word	Noun	Adjective	Verb	Adverb
midriff	Yes	No	No	No
midsection	Yes	No	No	No

As nouns, midriff and midsection are synonyms defined as:

midriff and midsection: the middle area of the human torso (usually in front)

Other synonyms of midriff include middle.

midriff (noun)	midsection (noun)
(anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration	the middle area of the human torso (usually in front)
the middle area of the human torso (usually in front)