Noun, pl. chromosomes
1. A structure within the cell that bears the genetic material as a threadlike linear strand of DNA bonded to various proteins in the nucleus of eukaryotic cells, or as a circular strand of DNA (or RNA in some viruses) in the cytoplasm of prokaryotes and in the mitochondrion and chloroplast of certain eukaryotes. (biology-online.org)
2. A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. (Google Dictionary)
3. (Biology, Cytology)
A structure in the cell nucleus that contains DNA, histone protein, and other structural proteins. (wiktionary.org)
Word origin: 19th century: from German Chromosom, ultimately from Ancient Greek χρῶμα (khroma, “colour”) + σῶμα (“body”) (because they are stained under the microscope).