A nuclease is an enzyme capable of cleaving the phosphodiester bonds between the nucleotide subunits of nucleic acids. Older publications may use terms such as "polynucleotidase" or "nucleodepolymerase".
Nucleases are usually further divided into endonucleases and exonucleases, although some of the enzymes may fall in both categories.
Read more about Nuclease: Introduction, Endonucleases and DNA Fragments, Endonucleases and Sticky Ends