The word "deoxyribonucleic" refers to a type of molecule found in living organisms like humans. It carries genetic information that determines our traits and characteristics. It is often abbreviated as DNA. Full definition
The inherited master plan of the cell is contained in the molecules of deoxyribonucleic acid. (scientificamerican.com)
The relatively recent emergence of biophysics as a scientific discipline may be attributed, in particular, to the spectacular success of biophysical tools in unravelling the molecular structure of deoxyribonucleic acid (DNA), the fundamental hereditary material, and in establishing the precisely detailed structure of proteins such as hemoglobin in order that the position of each atom may be known. (britannica.com)
DNA stands for deoxyribonucleic acid, it's a long thin molecule a bit like a recipe containing instructions or code which tells cells how to behave and grow. (science-sparks.com)