something that is handed out or given away free of charge.
2 n. & adj. — Hockey
loss of the puck that directly results in a goal against one's own team.
Type: 4. Culturally Significant — The hockey meaning is an expansion of meaning 1. While found in other sports as well, the term is particularly frequent in the hockey context, perhaps on account of the speed of the game. Like other hockey terms, giveaway carries some cultural significance.
COD-2 defines the term more broadly, as a turnover of the puck, and does not label it as Canadian.