(of a liquid) to move around noisily in the bottom of a container, or to cause liquid to move around in this way by making rough movements: (Cambridge Dictionary)
The slap or splash of liquid. (Merriam – Webster)
To flounder or splash through water, mud, or slush. (Merriam – Webster)
To splash or move through water, mud, or slush. (Dictionary.com)
(of a liquid) to move about actively within a container. (Dictionary.com)
If a liquid sloshes around or if you slosh it around, it moves around in different directions. (Collins Dictionary)
(of liquid in a container) move irregularly with a splashing sound. (Oxford Dictionaries)
Dirtbag Diaries Podcast: A Slosh in the Bucket.
Three-dimensional dynamic liquid slosh in partially-filled horizontal tanks subject to simultaneous longitudinal and lateral excitations.