Using -ish at the end of most adjectives describes something without being specific. With some words, using -ish may not sound a bit odd and wouldn't be used. For example, it's okay to say: "sharpish", but it doesn't sound right to say "brokenish". Some words naturally allow us to say -ish at the end, and some don't, because it sounds odd. If they are used in an odd way, it's likely because the speaker wanted to sound humourous.

ish is used instead of "approximate" in sentences, to mean "not totally/fully". For example, "it is sunny ish" means there is 90% sun/or nearly sunny except for a few clouds. Or "It is red ish colour" means it slightly off colour/ or dark orange/pinky say but nearly fully red.