this·tle·down 
(thĭsəl-doun′)
(thĭsəl-doun′)n.
The silky down attached to the seedlike fruit of a thistle.
- superclass
- supercluster
- supercoil
- supercollider
- supercolony
- supercomputer
- superconduct
- superconducting
- superconductive
- superconductivity
- superconductor
- supercontinent
- supercool
- supercritical fluid
- supercurrent
- superdelegate
- superdense
- superdominant
- superduper
- superego
- supereminence
- supereminent
- supereminently
- supererogate
- supererogation