tert-Butyldimethylsilyl chloride is an organosilicon compound with the formula (MeC)MeSiCl (Me = CH). It is commonly abbreviated as TBSCl or TBDMSCl.  It is a chlorosilane containing two methyl groups and a tert-butyl group. As such it is more bulky that trimethylsilyl chloride.  It is a colorless or white solid that is soluble in many organic solvents but reacts with water and alcohols.  The compound is used to protect alcohols in organic synthesis.  
tert-Butyldimethylsilyl chloride reacts with alcohols in the presence of base to give tert-butyldimethylsilyl ethers: 
:(MeC)MeSiCl  +  ROH  →   (MeC)MeSiOR  +  HCl
These silyl ethers hydrolyze much more slowly than the trimethylsilyl ethers.
It also can silylate terminal alkynes.