1.
vanity, conceit, self-flattery
An excessively high opinion of oneself, especially regarding one's appearance, abilities, or worth.
Related verb
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
The kanji 自惚れ is standard, but hiragana うぬぼれ is also used.