Alastair is a unique and distinct name that may not have many synonyms. However, there are a few similar names that bear resemblance to it. Some of the synonyms for Alastair include Alexander, Alistair, Alasdair, and Alister. These names have a similar origin and meaning as Alastair, which is "defender of the people". Alexander is a Greek name that means "defender of the people", Alistair is a Scottish name that means "defender of mankind", Alasdair is a Gaelic name meaning "defender of men". These names can be considered as alternate options if Alastair is not available for naming a baby.