May I suggest a third design?

NamesAndAliases
NAA_id	Name	Definition_id
1	Foo	1
2	Foo_bis	1
3	Bar	2

Definitions
Def_id	Definition
1	A Foo-ish thing
2	A Bar-ish thing

All names and aliases are in one table, if you wish, you can add another column to distinguish between names and aliases, although I see no real necessity.

All definitions are in a second table, so updating this table automatically updates the definitions of all related names and aliases.

Update: I only now see that I said the same as the AM in Re: OT: benefits of database normalization