busy tone
originally US
noun
A sound indicating to a caller that a telephone line is engaged.
Origin
Early 20th century.
- understaffing
- understairs
- understand
- understandability
- understandable
- understandably
- understander
- understanding
- understandingly
- under starter's orders
- understate
- understated
- understatedly
- understatement
- understater
- under steam
- understeer
- understocked
- understood
- understored
- understorey
- understrapper
- under-strength
- understructure
- understudy