1. The feeling of being an old man when you really aren't. To feel very very old compared to your actual age.
2. To have bodily pains which aren't that bad but make you feel old.
3. To feel old compared to the people in your life.
4. Staying inside and not going out, while regaling of your youthful days.
5. To look like an old man and/or feel like an old man.
1. After finding out he was seven years older than everyone else at his work, John had a severe case of old man syndrome.
2. After a summer of being a hermit, Jane had a serious case of old man syndrome.
Whiplash of the ass
From Futurama season 2, episode 11: "The Lesser of Two Evils"
Bender: I think I got whiplash!
Leela: You can't have whiplash, you don't even have a neck.
Bender: I meant ass whiplash!