Dated and sensitive term for cleft lip. Modern medical and everyday language prefers 口唇裂 (こうしんれつ) or 唇裂 (しんれつ). This word is now rarely used and may be considered insensitive.
See also: 口唇裂
It used to be called 'iguchi' (harelip), but now it's called 'koushinretsu' (cleft lip).
Kanji spelling using 兎 (rabbit) and 唇 (lip); a dated term for cleft lip. The reading いぐち is a gikun/jukujikun.
Kana spelling; may be used to avoid the dated kanji or for clarity.
Alternate kanji spelling using 欠 (lack); also dated and rare.
The kanji 兎唇 literally means 'rabbit lip', reflecting the visual similarity to a rabbit's split upper lip. The reading いぐち is a jukujikun (special kanji reading) not derived from the individual kanji's standard readings.