A chromosome having one very long arm and one extremely short arm is called

In the acrocentric chromosome, the centromere is situated close to its end, forming one extremely short and one very long arm.

Every chromosome (visible only in dividing cells) essentially has a primary constriction or the centromere.

The centromere holds two chromatids of a chromosome. Based on the position of the centromere, the chromosomes can be classified into four types.

The metacentric chromosome has a middle centromere forming two equal arms of the chromosome.

 The sub-metacentric chromosome has a centromere slightly away from the middle of the chromosome, resulting in one shorter arm and one longer arm. 

The Telocentric chromosome has a terminal centromere.