Scumhunting is the process of trying to find scum, typically via either paying attention to statements made by other players during the Day ("passively" scumhunting), or via actively asking questions to observe the replies ("actively" scumhunting). Because determining the membership of each faction is typically critical to the town's victory chances, town players normally spend most of the game scumhunting, and the scum often have to pretend to scumhunt in order to fit in.
In a multiball setup, scum have a reason to scumhunt: they don't know the membership of the other faction, and benefit from this information. Such games often make scumhunting more difficult, because the scumtell of "lack of/nongenuine scumhunting" is less likely to occur.
The alternative to scumhunting is townhunting; after identifying enough townies, it is possible to determine who the scum are through a process of elimination. This is a less popular strategy, especially in larger games (in which scum benefit more from the fact that knowledge of who is generally perceived as town helps them aim their nightkill, and in which more townies have to be found to figure out the scum), but is seen on occasion. Townhunting becomes increasingly powerful as the game gets smaller, becoming about equal in strength to scumhunting at LyLo.