Viññatti: lit. 'making known' 'intimation', is an Abhidhamma term for bodily expression kāya-viññatti and verbal expression vacī-viññatti both belonging to the materiality-group. They are produced by the co-nascent intention, and are therefore, as such, purely physical and not to be confounded with kamma, which as such is something mental. Cf. Kath. 80, 100, 101, 103, 194 see: Guide V. - App..
One speaks of 'bodily expression', because it makes known an intention by means of bodily movement, and can itself be understood by the bodily movement which is said to be material.
'Verbal expression' is so called because it makes known an intention by means of a speech-produced noise; Vis.M XIV.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.