rat-a-tat-tat 
(răt′ə-tăt′tăt)
(răt′ə-tăt′tăt)n.
A series of short sharp sounds, as that made by knocking on a door.
[Imitative.]
- second-rateness
- second-rater
- second sight
- second-story man
- second-strike
- second string
- second-string
- second-stringer
- second thought
- second wind
- Second World
- Second-World
- Second World War
- secrecy
- secret
- secreta
- secretagogue
- secretarial
- secretariat
- secretary
- secretary bird
- secretary-general
- secretary of state
- secretase
- secret ballot