Acrocentric

They are typed as telocentric acrocentric

acrocentric chromosome

An acrocentric is a chromosome which has the centomere, the central region, closer to one end than the other, thus having one short arm and one long arm.

A chromosome is determined to be metacentric, acrocentric or telocentric by the location of its centromere. Centromeres are the point of attachment of two sister chromatids. Sister chromatids are formed during DNA replication prior to mitosis or meiosis. Chromosome Y by itself (when it is not replicating and there are no sister chromatids) is not acrocentric, as it wouldn't even have a centromere location.