(a kind of) (semi-)liquid preparation served with food to give flavour; rude remarks (often more amusing than annoying)
condiment
Cases of word usage
1) (the process of using) a sauce for food; (the process of using) something to dress (dressing)
2) (a sauce made using) the juice which comes from meat while it is cooking (gravy)
3) a red sauce made from tomato juice (ketchup)
4) (a plant with yellow flowers and seeds that produce) a fine, yellow powder, made into hot sauce (mustard)