Alaster \a-las-ter, al(a)-ster\ as a boy's name is a variant of Alastair (Greek) and Alexander (Greek), and the meaning of Alaster is "man's defender; man's defender, warrior".

The baby name Alaster sounds like Alyster, Allaster, Alister, Alester, Alaister, Alastor and Alasteir. Other similar baby names are Allyster, Allister, Allastir, Alistar, Aleister, Alistir, Alsten and Alter.