Quoted from: Glossary of Telecom Marketing Terms | Telecom Marketing

UMA – Unlicensed Mobile Access - Provides access to cellular mobile voice and data services over unlicensed spectrum technologies, such Bluetooth or Wi-Fi (802.11). A UMA phone can use a cellular networks (GSM, CDMA, etc.) when out and about, and automatically switch to a UMA-enabled Bluetooth or Wi-Fi local network when in range, such as at home or in the office.