If a person is desperate, he or she has a strong need for something. A situation requires immediate attention. The word "desperate" is an adjective:
Jonah can’t find a good apartment. He’s becoming desperate.
Renee is desperate to find a new job. She lost her job six months ago, and now she’s desperately trying to find employment. (The word "desperately" is an adverb.)
A desperate man walked into the bank and stole some money. He was quickly caught afterwards.
People in the village have a desperate need for clean water. They desperately need it.
An "ion" ending creates the noun form for this word:
Desperation filled the air as a small kitchen fire quickly spread out of control.
Renee’s desperation to find a new job is evident to all who know her.
A sense of desperation suddenly took hold among the passengers in the sinking ship.
a sinking ship