Concise Bible Dictionary:

Those who dwell in a house under one head, including the wife and children, and embracing servants who were usually slaves (Gen. 15:2-3; Luke 12:42; Acts 10:7; Phil. 4:22). We read of the baptism of whole households (Acts 16:15; 1 Cor. 1:16). The Lord speaks of His disciples as His household (Matt. 10:25); and saints are called the “household of faith,” and the “household of God” (Gal. 6:10; Eph. 2:19).