Concise Bible Dictionary:
A forest on the east of the Jordan where the battle was fought against Absalom, and where he was killed. It is said that the wood devoured more people than the sword, probably referring to swamps, morasses, and pits, for Absalom’s body was thrown into a “great pit” (2 Sam. 23:6-17). Why the place was called “Ephraim’s Wood” is not known.