Refers to a person who has lost in competition, life, or social standing. Often carries a pitiful or contemptuous nuance, like a 'beaten dog'. Can also be used for someone who is habitually unsuccessful.
After losing the election, he looks completely like a loser.
Throw away that loser mentality and try again.
unmarried and childless older woman
Slang, derogatory. Popularized by the book '負け犬の遠吠え' (The Howl of the Loser Dog). Refers to an unmarried, childless woman over 30, implying she has 'lost' in the societal game of marriage and family.
See also: お一人様 (おひとりさま)
The term 'makeinu' is sometimes criticized as a discriminatory label against unmarried women.
I wish people would stop treating him like a loser.
Even in her 30s, an unmarried woman is sometimes called a 'makeinu'.
If I keep doing nothing, I'll end up a loser.
She was depressed, thinking of herself as a loser.