Source: Jeppesen Chart Tutorial

MEA Minimum Enroute Altitude
 The minimum altitude between radio fixes, usually plotted above or below the route box, such as "←10000 8000→", "←6500", "→9900"; arrows indicate the direction of flight.

MOCA Minimum Obstruction Clearance Altitude
 The published effective minimum obstacle clearance altitude between radio fixes, indicated by altitude and the suffix "T", such as 1300T.

Enroute MORA Enroute Minimum Off Route Altitude
 Provides obstacle clearance clearance within 10 nautical miles of the route centerline and fixes, indicated by altitude and the suffix "a", such as 1300a.

MAA Maximum Authorized Altitude
 The highest usable altitude or flight level published for a airspace or route segment (due to technical limitations, ground-based navigation equipment limitations, etc.), indicated by altitude and the prefix "MAA", such as MAA 25000 or MAA FL240.

MCA Minimum Crossing Altitude
 The minimum flight altitude required to cross certain fixes when an aircraft transitions from a route segment with a lower MEA to a segment with a higher MEA, indicated by altitude, route, direction, and the prefix "MCA", such as "MCA V-283-372 7400E" indicating a minimum crossing altitude of 7400 feet for eastbound flight along V-283 or V-372.

MRA Minimum Reception Altitude
 The minimum altitude at which intersection position can be determined, indicated by altitude and the prefix "MRA", such as MRA 9500.