noun
peat
PEET/piːt/
Partly decayed plant matter used as fuel or to improve soil.
Dark, fibrous peat lies beneath the living moss.

Etymology
The word first referred to a cut piece of turf, rather than the partly decayed plant material itself. Its origin is unknown, though a Celtic connection is probable.
In context
peat bogs will subside as a result of sediment being buried on top. That will exclude all oxygen to prevent any further decay.
More examples
- The bog preserved plant remains in the peat.
- Workers once cut peat into blocks for fuel.
- Draining the wetland exposed its peat to the air.
Forms
peat