Definition of ballast
(Entry 1 of 2)
1
: a heavy substance (such as rocks or water) placed in such a way as to improve stability and control (as of the draft of a ship or the buoyancy of a balloon or submarine)
tossed several tons of ballast overboard
2
: something that gives stability (as in character or conduct)
She provided the ballast we needed during stressful times.
3
: gravel or broken stone laid in a railroad bed or used in making concrete
4
: a device used to provide the starting voltage or to stabilize the current in a circuit (as of a fluorescent lamp)
in ballast
of a ship
: having only ballast for a load
ballast
verb
ballasted; ballasting; ballasts
Definition of ballast (Entry 2 of 2)
1
: to steady or equip with or as if with ballast
They ballast the canoe with large rocks.
2
: to fill in (something, such as a railroad bed) with ballast (see ballast entry 1 sense 3)
Test Your Vocabulary
Name That Food
-
- Name these cookies!

Can you spell these 10 commonly misspelled words?
TAKE THE QUIZ
A daily challenge for crossword fanatics.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Share ballast
Time Traveler for ballast
The first known use of ballast was in the 15th century
See more words from the same century