Warning, this verb may not exist. Conjugation is given as example.
Indicative
Present
I stiffer you stiffer he stiffers we stiffer you stiffer they stiffer
Present continuous
I am stiffering you are stiffering he is stiffering we are stiffering you are stiffering they are stiffering
Preterite
I stiffered you stiffered he stiffered we stiffered you stiffered they stiffered
Preterite continuous
I was stiffering you were stiffering he was stiffering we were stiffering you were stiffering they were stiffering
Present perfect
I have stiffered you have stiffered he has stiffered we have stiffered you have stiffered they have stiffered
Present perfect continuous
I have been stiffering you have been stiffering he has been stiffering we have been stiffering you have been stiffering they have been stiffering
Pluperfect
I had stiffered you had stiffered he had stiffered we had stiffered you had stiffered they had stiffered
Pluperfect continuous
I had been stiffering you had been stiffering he had been stiffering we had been stiffering you had been stiffering they had been stiffering
Future
I will stiffer you will stiffer he will stiffer we will stiffer you will stiffer they will stiffer
Future continuous
I will be stiffering you will be stiffering he will be stiffering we will be stiffering you will be stiffering they will be stiffering
Future perfect
I will have stiffered you will have stiffered he will have stiffered we will have stiffered you will have stiffered they will have stiffered
Future perfect continuous
I will have been stiffering you will have been stiffering he will have been stiffering we will have been stiffering you will have been stiffering they will have been stiffering
Conditional
Present
I would stiffer you would stiffer he would stiffer we would stiffer you would stiffer they would stiffer
Present continuous
I would be stiffering you would be stiffering he would be stiffering we would be stiffering you would be stiffering they would be stiffering
Past
I would have stiffered you would have stiffered he would have stiffered we would have stiffered you would have stiffered they would have stiffered
Past continuous
I would have been stiffering you would have been stiffering he would have been stiffering we would have been stiffering you would have been stiffering they would have been stiffering