1. Operation on something past or preceding 
2. Action returned, or action backward

Derived forms: retroactions

• long since
• long sleeve
• long suit
• long tom
• long ton
• long trousers
• long underwear
• long wave
• long weekend
• long whist
• long-acting
• long-armed
• long-billed marsh wren
• long-bodied
• long-branched
• long-chain
• long-chain molecule
• long-clawed prawn
• long-dated
• long-distance
• long-distance call
• long-distance runner
• long-drawn-out
• long-eared bat
• long-eared owl