1.
vanity, conceit, self-flattery
An excessively high opinion of oneself, especially regarding one's appearance, abilities, or worth.
Related words
自惚れる (to be conceited, to flatter oneself) is the verb form. 自惚れ is the noun derived from it.
Usage
Always negative. Used to criticize someone who overestimates themselves. Common patterns include 自惚れが強い (has strong vanity) and 自惚れにすぎない (is nothing but conceit).
Writing
Often written in kana, うぬぼれ; the kanji spelling is less common (also 己惚れ).