- a helical spring used to hold closed a valve in the cylinder head of an internal-combustion engine
- any spring that closes a valve after it has been opened mechanically or by flow pressure
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Examples from the Web for valve spring
The engine had to be stopped three times, twice due to valve-spring collar failures and once due to a valve head breaking.