Desperate means "having lost all hope." If you are desperate for food, it means you are starving, possibly about to die. If you are in a desperate situation, it means things are really, really bad.
Desperate, desparate, or despirate? The word desperate is misspelled often enough that it's the despair of English teachers. Both desperate and despair come from the same Latin verb as despair. Don't mix it up with disparate, a totally different word that means "distinctive, different, various."