The waddle of ducks.
When a pregnant woman can't walk steadily and sways from side to side, this is an example of when she waddles.
The unsteady walk of a very-pregnant woman who shifts her weight from foot to foot as she walks is an example of a waddle.
Origin of waddle
- Frequentative of wade
From American Heritage Dictionary of the English Language, 5th Edition
- First known use in English in a version of the Song of Roland around the year 1400. (Source:OED online)