noun
Common colloquial term for earwax. The medical term is 耳垢 (じこう).
耳くそがたまっている。
Earwax has built up.
綿棒で耳くそを取る。
I remove earwax with a cotton swab.
Rare kanji form using 屎 (excrement); not commonly used.
Medical/formal term for earwax; 耳くそ is the everyday colloquial word.
Compound of 耳 (ear) and くそ (excrement/waste). The exact historical derivation is uncertain, but the word is transparently formed from these elements.