1. A reciprocal group action
   - return, paying back

Type of: group action

• acidulent
• acidulous
• acidulousness
• aciduric
• acinar
• acinic
• Acinonyx
• Acinonyx jubatus
• Acinos
• Acinos arvensis
• acinose
• acinous
• acinus
• Acipenser
• Acipenser huso
• Acipenser transmontanus
• Acipenseridae
• ack-ack
• ack-ack gun
• ackee
• acknowledge
• acknowledgeable
• acknowledged
• acknowledgement
• acknowledgment