Allysdair \a-llys-dair, all(y)-sdair\ as a boy's name is a variant of Alastair (Greek), and the meaning of Allysdair is "man's defender".
The baby name Allysdair sounds like Alysdair and Allystair. Other similar baby names are Alasdair, Alystair, Allistair, Alaisdair and Alisdair.