I prefer the meaning from the Volvo ad where they are crossing a small bridge on a tiny woodsy country lane and a troll comes out with a large club and asks them to answer three questions before they pass. Hilarious.
Or the Cave Adventure game (was it Zork?) where you reach, on foot, a stone bridge and a sign says 'Stop, Pay Troll'. You try and cross and a large troll ambles out from underneath.
Having picked up an axe previously on your adventures, you throw it at the Troll. He deftly catches it, examines it and hands it back, saying 'Sorry, not treasure quality!'
You leave and later find some coins to give to the Troll to let you across. After all, there is a room beyond that with a bear on a chain and a pot of gold within the bear's reach, if only you could distract the bear..