Having the ability to differentiate into all cell types.
For example, the zygote and early embryonic cells are totipotent since they can differentiate into any cell type during development.
Word origin: toti- » from Latin tōtus, entire + - potent, have power, to be able.
Related forms: totipotency (noun)
Compare: unipotent, multipotent, pluripotent.
See also: potent.