ribonucleic acid(n = noun.substance) rna - (biochemistry) a long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of a cell where it is associated with microsomes; it transmits genetic information from DNA to the cytoplasm and controls certain chemical processes in the cell; "ribonucleic acid is the genetic material of some viruses"
ribonucleic acid, n. a nucleic acid yielding ribose on hydrolysis, present in living cells, esp. in ribosomes where it is involved in protein synthesis.