Shovelware are games made fast and cheap and with very poor quality. It doesn't matter if they're mini-game collections or not (although since mini games can be cranked out fast, many shovelware games are minigame collections).
They get dumped onto retail shelves by the masses - think of a big pile of crappy games and someone is shoveling them onto the store shelves. Much like someone shoveling a big pile of manure from an animal pen.
as i said earlier, just cause it may be good doesn't mean it isn't shovelware.