* For attention to detail: Careless, sloppy, negligent, haphazard, casual
* For thoroughness: Superficial, cursory, perfunctory, incomplete, rushed
* For precision: Imprecise, inaccurate, inexact, approximate, rough
* For planning: Impulsive, spontaneous, unplanned, haphazard, chaotic
The best opposite word depends on the context of how "meticulous" is being used.