Altar - Vine's Expository Dictionary of New Testament Words
Altar[ 1,,G2379, thusiasterion ]
probably the neuter of the adjective thusiasterios, is derived from thusiazo, to sacrifice." Accordingly it denotes an "altar" for the sacrifice of victims, though it was also used for the "altar" of incense, e.g., Luke 1:11. In the NT this word is reserved for the "altar" of the true God, Matthew 5:23-Matthew 5:24; Matthew 23:18-Matthew 23:20, Matthew 23:35; Luke 11:51; 1 Corinthians 9:13; 1 Corinthians 10:18, in contrast to bomos, No. 2, below. In the Sept. thusiasterion is mostly, but not entirely, used for the divienely appointed altar; it is used for idol "altars," e.g., in Judges 2:2; Judges 6:25; 2 Kings 16:10.
[ 2,,G1041, bomos ]
properly, "an elevated place," always denotes either a pagan "altar" or an "altar" reared without Divine appointment. In the NT the only place where this is found is Acts 17:23, as this is the only mention of such. Three times in the Sept., but only in the Apocrypha, bomos is used for the Divine altar. In Joshua 22 the Sept. translators have carefully observed the distinction, using bomos for the altar which the two and a half tribes erected, Joshua 22:10-Joshua 22:11, Joshua 22:16, Joshua 22:19, Joshua 22:23, Joshua 22:26, Joshua 22:34, no Divine injunction being given for this; in Joshua 22:19, Joshua 22:28-Joshua 22:29, where the altar ordained of God is mentioned, thusiasterion is used.