Definition
MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)
The lowest published altitude in effect between radio fixes on VOR airways, off‐airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which assures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.
Source: FAA Pilot/Controller Glossary (verbatim from the Federal Aviation Regulations).