X chromosome

noun, Genetics.
1.
a sex chromosome of humans and most mammals that determines femaleness when paired with another X chromosome and that occurs singly in males.
Compare Y chromosome.
Origin
1910-15
British Dictionary definitions for x-chromosome

X-chromosome

noun
1.
the sex chromosome that occurs in pairs in the diploid cells of the females of many animals, including humans, and as one of a pair with the Y-chromosome in those of males Compare Y-chromosome
x-chromosome in Medicine

X-chromosome n.
The sex chromosome associated with female characteristics, occurring paired in the female and singly in the male sex-chromosome pair.

x-chromosome in Science
X-chromosome
  (ěks'krō'mə-sōm')   
The sex chromosome that in female mammals is paired with another X-chromosome and in males is paired with a Y-chromosome. Very few genes on the X-chromosome have counterparts on the Y-chromosome, and since males have only one X-chromosome, any gene present on it (even if the gene is recessive in females) is expressed in males. In females, one of the two X-chromosomes in each cell is deactivated. See more at sex chromosome. See note at sex.