Full Idea
I believe 'motion' to be definable, and the definition which says that it is 'change of place' deserves respect.
Gist of Idea
Maybe motion is definable as 'change of place'
Source
Gottfried Leibniz (New Essays on Human Understanding [1704], 3.04)
Book Reference
Leibniz,Gottfried: 'New Essays on Human Understanding', ed/tr. Remnant/Bennett [CUP 1996], p.297
A Reaction
This seems to be the 'at-at' view of motion, championed by Bertrand Russell. (At p1 at t1, at p2 at t2...). Leibniz's version only mentions space and not time, and it includes 'change', which would need definition without mentioning motion.