Baal (Βάαλ) is the Greek transliteration of Hebrew Baal (H1168), meaning "lord, master, owner." In the NT it appears once in Romans 11:4, where Paul quotes 1 Kings 19:18: God's word to Elijah that He had preserved 7,000 who had not bowed the knee to Baal.
Paul's citation of the Baal apostasy in Romans 11 makes a decisive argument about God's faithfulness to Israel. Just as Elijah thought he was the last faithful Israelite but was wrong — God had a hidden remnant — so in Paul's day, Israel's widespread rejection of the gospel did not mean God had abandoned His people. God always preserves a remnant. The Baal worship crisis was the theological low point of OT Israel; yet God's sovereign grace preserved His people. Similarly, rejection of Christ by many in Israel does not nullify God's covenant faithfulness.