The case of 马虎。
The HSK knows, on some level, that it graduates students who if they don't have solely a knowledge of language related terms, at least have a vocabulary top-heavy in school/language related words. Why does it know this? Because for some reason Marvel started letting Joss Whedon write X-men and one day all of a sudden the HSK had acquired consciousness and could fly around the world and do evil shit. No, wait, that's the danger room.
马虎 - 形 - careless, sloppy, not serious (不认真）, done 'sloppily', 'poorly', 'carelessly'
I see this stretched all the way to 'casually', which is a pretty big leap in english, but let's go there.
马马虎虎 - 1, same as 马虎
2, the oft-used and somewhat infamous 一般, which is taught as the rarely used by english speakers 'so-so’， more properly rendered as 'ok' with an emphasis on the 'not that great'
刻苦 - kèkǔ - 形 - hardworking, on the same with 勤奋, with both of them being stronger than 用功
勤奋 － qínfèn - 形 - not very 口语, but you will see it written often. - diligent
粗心大意 - cūxīndàyì - 形 - 算是口语或“习惯用语”，at least according to the HSK, careless, sloppy
note that 粗心 and 大意 also both independently mean careless, sloppy
Don't worry about usage, just know these words and you'll be fine.
含糊 - hánhu - 形 - 马虎， careless, sloppy