Pronounced like onion with 'Gr' in front, and usually in the plural.
Singular: - A left (or right) sailor's testicle that has been grossly inflated by a true 'blow' job in some stinking back-street Asian or Arab port during shore leave.
Plural - (Gronions) The worst scenario. Both balls about to explode through over-inflation, usually brought about by the aforesaid vicious fellatio, but with the added intervention of the house madam sticking a finger up the rectum at the same time.
'You seem to have a severe case of the Gronions'.
'Is there any cure?'
'No; but if you're willing, I suggest you donate one to Arsenal and the other to Man. U.'