Transposon. Definition. noun, plural: transposons. A small segment of DNA that is capable of replicating and inserting copies of DNA at random sites in the same or a different chromosome.Supplement.Transposons are DNA segments that are mobile.They can replicate and insert copies at sites within the same or a different chromosome. They can therefore alter the genetic constitution of an organism. Transposons have two types according to the genes they code for: (1) simple transposons and (2) complex transposons.ransposons are DNA segments that are mobile. They can replicate and insert copies at sites within the same or a different chromosome. They can therefore alter the genetic constitution of an organism. Transposons have two types according to the genes they code for: (1) simple transposons and (2) complex transposons.