An eight letter word for put under stress is "strained."
irritate
assassin
assassin
distress, browbeat, threaten
"Stress out"? That's not really much of a word, more of a phrase. "Stressing out" means when your put under too much pressure or stress than you can bare.
1. P 2. R 3.e 4.s 5.s 6.u 7.r 8.e
Assuming you mean "surprising", you put the stress on the second syllable.
this type of energy is used when the body is put under stress
You can put the stress mark on the second syllable of the word "volunteer," so it is pronounced as vol-un-TEER.
Hez - i - teyt - stress on Hez
There is slightly more stress of the "For" part.