noun
sick friend; fellow patient
Refers to a friend who is ill, or to someone one meets and befriends while both are patients. The context usually makes the intended meaning clear.
入院中にできた病友と、退院後も連絡を取り合っている。
I still keep in touch with a fellow patient I met while hospitalized.
彼は病友を見舞うために、毎週病院へ通っている。
He goes to the hospital every week to visit his sick friend.