A combi is a machine or a vehicle that does two or more jobs in one. You meet the word most on product labels, not in everyday chat: a combi boiler both heats the house and gives hot water; a combi van can carry people and also carry goods; a combi oven cooks in more than one way. Makers like the short form because it looks neat on a box. Though actually, people do not walk around calling any two-use thing “a combi”; they say it when the company has already put Combi on the name. Younger speakers may say combo for a mix (a meal combo). That is close in feeling, but combo is casual talk about mixing, while combi is the product-name word for a two-in-one machine or vehicle.