Example: In Battlefield:Modern Combat, one Achievement acquired by hitting 5 enemies and 0 friendlies in one mortar strike. This is doable but, during normal play, exceptionally hard. Boosting would be getting 5 people you know to join the other team and all stand in one place so you could drop a mortar strike and get the achievement.
"Stop boosting your car, it makes my lil 4 cyl rice burner look like a bagger".
(Me)"My car has boost, I can't help that Im constantly boosting it. It's fun!"