Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I might stiffer you might stiffer he might stiffer we might stiffer you might stiffer they might stiffer
V-ing form
I might be stiffering you might be stiffering he might be stiffering we might be stiffering you might be stiffering they might be stiffering
Perfect
I might have stiffered you might have stiffered he might have stiffered we might have stiffered you might have stiffered they might have stiffered
V-ing perfect
I might have been stiffering you might have been stiffering he might have been stiffering we might have been stiffering you might have been stiffering they might have been stiffering
Negation
Simple form
I mightn't stiffer you mightn't stiffer he mightn't stiffer we mightn't stiffer you mightn't stiffer they mightn't stiffer
V-ing form
I mightn't be stiffering you mightn't be stiffering he mightn't be stiffering we mightn't be stiffering you mightn't be stiffering they mightn't be stiffering
Perfect
I mightn't have stiffered you mightn't have stiffered he mightn't have stiffered we mightn't have stiffered you mightn't have stiffered they mightn't have stiffered
V-ing perfect
I mightn't have been stiffering you mightn't have been stiffering he mightn't have been stiffering we mightn't have been stiffering you mightn't have been stiffering they mightn't have been stiffering
Interrogative form
Simple form
might I stiffer? might you stiffer? might he stiffer? might we stiffer? might you stiffer? might they stiffer?
V-ing form
might I be stiffering? might you be stiffering? might he be stiffering? might we be stiffering? might you be stiffering? might they be stiffering?
Perfect
might I have stiffered? might you have stiffered? might he have stiffered? might we have stiffered? might you have stiffered? might they have stiffered?
V-ing perfect
might I have been stiffering? might you have been stiffering? might he have been stiffering? might we have been stiffering? might you have been stiffering? might they have been stiffering?
Interro-negative form
Simple form
mightn't I stiffer? mightn't you stiffer? mightn't he stiffer? mightn't we stiffer? mightn't you stiffer? mightn't they stiffer?
V-ing form
mightn't I be stiffering? mightn't you be stiffering? mightn't he be stiffering? mightn't we be stiffering? mightn't you be stiffering? mightn't they be stiffering?
Perfect
mightn't I have stiffered? mightn't you have stiffered? mightn't he have stiffered? mightn't we have stiffered? mightn't you have stiffered? mightn't they have stiffered?
V-ing perfect
mightn't I have been stiffering? mightn't you have been stiffering? mightn't he have been stiffering? mightn't we have been stiffering? mightn't you have been stiffering? mightn't they have been stiffering?