M
- MAC Address (Media Access Control Address)
- Maintenance Access
- Maintenance Window
- Man-in-the-Middle Attack (MITM)
- Managed Services
- Manual Call Distribution (MCD)
- Maximum Transmission Unit (MTU)
- Media Access Control (MAC)
- Media Gateway
- Media Server
- Media Termination Point (MTP)
- Meet-Me Conference
- Message Passing
- Message Queue
- Message Waiting Indicator (MWI)
- Microphone
- Middleware
- Migration
- Mobile Device Management (MDM)
- Mobile Extension
- Mobile VoIP
- Modem (Modulator-Demodulator)
- Modular Jack
- Monitoring
- Monitoring and Reporting
- MPLS VPN
- Multicast
- Multiline
- Multiplexing
- Multipoint Control Unit (MCU)
- Multiprotocol Label Switching (MPLS)
- Music on Hold (MoH)
