Strictly speaking, the accepted term for clearance between mechanical components, especially with respect to the mating teeth of a geartrain, is 'backlash'. At Dictionary.com, I found this etymology:
'backlash 1815, of machinery, from back (adj.) + lash. In metaphoric sense, it is attested from 1921.'
It seems to me that the 'back' portion of 'backlash' introduces a needless specificity to the term for many purposes. Hence, I'm inclined to simply use the word 'lash' as a catch-all term for any sort of clearance/play/slop in a mechanical relationship, even though I can find no authoritative support for that usage. Though I tend to be a stickler about correct, authoritative word usage, in this particular case I'm entirely at ease with taking the attitude, "Authority? We don't need no stinking authority!"
# # #
# # #
