Official. A Soldier, Highly trained in Modern Combat Warfare capable of fighting as an Infantry Soldier, with the added responsibility of the disposal of Explosive Ordinance Devices (EOD), Minefield Laying/Clearance, Defensive Protection, Installing and Removing Bobby Traps, Removal of Improvised Explosive Devices (IED), Bridge Building, and Construction. They are deployed with and Special Operations, Peacekeeping, Civil Emergencies.
Unofficial. The dude who blows shit up, The dude at the front, The One that's got "Follow Me" on the back of his shirt, The dude you don't want to fuck with.
Sapper is a light Army combat engineer, who has mastered the art of patrolling, demolition, and other light fighting commando style tactics. Sappers are bad ass and are equal to, if not better then Rangers. Sappers are often attached to infantry groups or Ranger operations to provide engineer expertise in demolition, booby traps and reconnaissance.
The term Sapper is derived from the word sap, as in digging (sap) of Dark and Middle ages fortification's and is now used for a wide range of specific Military and Civil trades.
In the Military generally a Sapper is a highly trained combat engineer, tradesperson, plant operator or fireman. In civilian occupations a Sapper is in most cases a fireman.
Its a Saturday, the sappers are out in town with their boyfriend's credit card to buy stupid clothes to wear that evening when said boyfriend is obligated to buy the sapper champagne, keeping with the whole "Footballers' Wives" fantasy.