Definitions

1. adjective

not requiring or using a storage tank; especially, using heat directly from a water heater or boiler without storing it in a tank

“Our new tankless water heater is a space-saving solution for our small apartment.”

2. noun

a water heater that does not store water in a tank, but heats it directly as needed

“We’re considering installing a tankless water heater to replace our old traditional model.”