persistent
1 adj Something that is persistent continues to exist or happen for a long time; used especially about bad or undesirable states or situations.
His cough grew more persistent until it never stopped...
2 adj Someone who is persistent continues trying to do something, even though it is difficult or other people are against it. ...a persistent critic of the government's transport policies...
persistent vegetative state (persistent vegetative states plural )If someone is in a persistent vegetative state, they are unable to think, speak, or move because they have severe brain damage, and their condition is not likely to improve. (MEDICAL) n-count