Boyd’s Bible Dictionary:
Used variously (Psa. 18:42; Isa. 57:20; Jer. 38:6; John 9:6); for making pottery (Isa. 41:25); for brick-making (2 Sam. 12:31); for sealing (Job 38:14); for writing tablets.
Strong’s Dictionary of Hebrew Words:
Meaning:
from 5666; properly, compact (part of soil), i.e. loam