Loser
noun
You've hopefully come across 負ける by now, which means "to lose." So, you can figure out this word means "losing dog." Well, calling someone a dog isn't so nice, so you're probably just calling them a loser.
The readings are kun'yomi, but you should be familiar with 負ける and of course 犬 well enough to learn the reading here.
自分が、一日中家にいて、テレビばっかりみてる負け犬だってことは自かくしているよ。
I'm aware that I'm a loser who loves to just stay home and watch TV all day.
あの負け犬が明日からおれの仕事を引きつぐとか、本当にがまんできないよ。
I can't stand the fact that the loser is taking over my job tomorrow.
この負け犬め!キモいんだよ!
You are a loser and really creepy!