Also called a Rubber Johnny, Sheath, Prophylactic or Durex(tm).
A small latex bag worn over the erect penis during sexual intercourse. This acts a barrier to either infection from a sexually transmitted disease (STD) or to prevent you making the tart you just shagged pregnant.
The condom can be of any colour, shape, ribbed, with lumps, ticklers and may even have GPS satellite communications. Some have even played tunes at the moment of ejaculation ie She'll be coming round the mountain when she comes. ..... I'll get my coat!
This differs from the Femi-dom which was a large carrier bag inserted in to a woman for the same purpose. Also known as shagging the bag.
Stories of teens using empty crisp bags and/or Tesco's carrier bags as condoms may or may not be true ... just dont want to think about that.
To use two condoms as extra insurance against STDs or pregnancy.
Apart from the obvious use in war ie Hearts and Minds ops with liberated lady civis, the condom has been used to cover the open end of a gat to ensure it doesnt fill with water ie Vietnam and any amphibious landing (just dont ask what the Royal Marines do with the spares!).