›[T]to use something different or new instead of another thing: substitute sth for sthIndustry must reduce fuel consumption by substituting alternative fuels for fossil fuels.substitute sth with sthIt takes time to substitute local brands with your own brand names.
substitute for sb[I]›WORKPLACEto take the place of another person or do their job for a period of time: She was asked to substitute for the absent committee chairman.
substitute for sth[I]›to do the same job as another thing or take its place: The government expects natural gas to substitute for oil exports in the future.Many dot.com companies have learnt that technology can never substitute for customer service.