Chain breeding
From Bulbapedia, the community-driven Pokémon encyclopedia.
Chain breeding is the process of breeding a move to a Pokémon that can only learn it as an egg move, then in turn using that Pokémon to breed it to another Pokémon that can learn the move as an egg move, but cannot breed with the original Pokémon.
An example of a move that is required to be chain bred would be Outrage.
| Grandparents |  Dragonite♂ (with Outrage) |
 Charizard♀ |
? | ? |
|---|---|---|---|---|
| Parents |  Charmander♂ (with Outrage) |
 Tyranitar♀ | ||
| Child |  Larvitar♀/♂ (with Outrage) | |||
Though to get a Tyranitar with Outrage requires only one intermediate Pokémon, making it a short chain, not all breeding chains are like this. In fact, some are several steps long, and at each stage, require the hatched egg to be a male Pokémon as to pass on the move to his own children.
