retaining valve
Word Rarity
Rare
Frequency: Zipf frequency 3.62 in modern English
21
Scrabble Score
14
Letters
4
Syllables
9
Unique Chars
Meaning
noun
A device that retains some air pressure in a train's air brake cylinders even when the automatic brake valve is set to the fully-released position, used on steep downgrades to allow a degree of continuous braking effort to be maintained without depleting the pressure in the train's brakepipe (which would result in the loss of nearly all braking ability, causing a runaway).