Boyd’s Bible Dictionary:
(burnt in). Ancient ink heavy and thick and carried in an ink-horn (Jer. 36:18; Ezek. 9:2).
Concise Bible Dictionary:
We know from the papyrus rolls discovered in Egypt that writing with pen, or reed, and ink was practiced in early days. Jeremiah caused Baruch to write in a book with ink the denunciations against Israel and Judah (Jer. 36:18). The horn that contained the ink was carried in the girdle, as it is in some parts of the East to this day (Ezek. 9:2-3,11).
Strong’s Dictionary of Hebrew Words:
Meaning:
from the same as 3563 (or as 7185); properly, a cup, i.e. an ink-stand