
A baby waves ta-ta.
Ta ta is defined as a British or informal way of saying goodbye.
An example of ta ta is when you wave your baby's hand and have him say "ta ta" to daddy.
ta-ta

Brit., Informal goodbye
Origin of ta-ta
origin, originally a child's termta-ta

interjection
Chiefly BritishUsed to express farewell.
Origin of ta-ta
Of baby-talk originta-ta

Interjection
- (chiefly UK, Australia, New Zealand, informal, colloquial) Goodbye.
Usage notes
Dated and rarely used in The United States, sometimes used in Canada. Although likely to be understood, it is likely to be considered rather humorous, particularly if used in a parody of British English speakers.
Anagrams
Origin
Probably derived from baby talk c1823 (imitative).