Dictionary of Biblical Words:
One of the temporary signs or gifts in the early church (1 Cor. 14) testifying by its evidently miraculous power to its Divine origin. This gift consisted in speaking fluently in a foreign tongue (not in no language at all, as is sometimes thought). Prophesying, or speaking by the Power of God to the conscience is put as a higher gift.
Boyd’s Bible Dictionary:
“And the whole earth was of one language, and of one speech”
(Gen. 11:1). Confusion of tongues and dispersion of peoples coincident (Gen. 11:7-9). “New tongues” (Mark 16:17), is the first notice of a gift specially characteristic of the first outpouring of the Spirit. Ten days afterward the promise was fulfilled in the Pentecostal phenomenon (Acts 2:1-13).