strap vs unstrap

strap is a noun but unstrap is not a noun.

Word	Noun	Adjective	Verb	Adverb
strap	Yes	No	Yes	No
unstrap	No	No	Yes	No

strap (noun)	unstrap (noun)
whip consisting of a strip of leather used in flogging
an elongated leather strip (or a strip of similar material) for binding things together or holding something in position
a band that goes over the shoulder and supports a garment or bag
hanger consisting of a loop of leather suspended from the ceiling of a bus or train; passengers hold onto it

strap (verb)	unstrap (verb)
secure (a sprained joint) with a strap	remove the strap or straps from
sharpen with a strap
tie with a strap
beat severely with a whip or rod