(part of common anime words)
Well, to begin with, the word kimochi 気持ち by itself means... "feeling." Yep, just "feeling," or "feelings," take a look:
- watashi no kimochi 私の気持ち
- kimi no kimochi 君の気持ち
- kono kimochi この気持ち
- kimochi wo tsutaeru 気持ちを伝える
To pass these feelings. (to have [someone] know how [you] feel)
.By the way, you can separate kimochi 気持ち into the words ki 気, which is a rather complicated word that's too difficult to explain and and mochi 持ち, which comes from the verb motsu 持つ, which means "to hold" or "to have." Yeah, it makes no sense.
Kimochi ii 気持ちいい
Next we have the word kimochi ii 気持ちいい, which isn't a word, but two words. The second one being ii いい.
Yes, ii いい is a word in Japanese. An adjective. It means "good." It even has a kanji, take a look: ii 良い.
Anyway, ii being "good" and kimochi being "feeling," one can conclude kimochi ii means "good feeling." Which is correct, sort of. To have a better idea, the following things are kimochi ii:
- ame ga kimochi ii 雨が気持ちいい
This rain feels good.
- massaji ga kimochi ii マッサージが気持ちいい
This massage feels good.
- hito wo tasukeru no wa kimochi ii 人を助けるのは気持ちいい
Helping people feels good.
- hito wo korosu no wa kimochi ii 人を殺すのは気持ちいい
Killing people feels good.
("tasty" food is oishii 美味しい, not kimochi ii)
Like any other adjective ending in -i -い, kimochi ii can also be conjugated to change in meaning slightly or to connect to other verbs.
- kimochi yokatta 気持ちよかった
It felt good. (in the past)
- kimochi yokute tamaranakatta 気持ちよくてたまらなかった
It felt so good I couldn't stop [doing it]
Kimochi warui 気持ち悪い
On the other side of the coin we have kimochi warui 気持ち悪い, which is actually on the other side of the coin since warui 悪い means "bad" and therefore kimochi warui means "bad feeling."
Plenty of bad things are kimochi warui, so for the love of all that is holy do not search for 気持ち悪い in Google Images. Do not do it. I mean it. Really. Just don't.
Like kimochi ii, kimochi warui is an adjective ended in -i -い that can be conjugated, and so on.
A shortened slang way of saying kimochi warui that's found in anime is kimoi キモい, or just kimo キモ.
It means literally the same thing as kimochi warui.