Baka (馬鹿 or バカ) is a Japanese word meaning "idiot" or "folly" or "trivial matter". "馬鹿" is composed of the Kanji "馬" (meaning "horse), and "鹿" (meaning "deer").
Numerous compounds and derivations exist including "馬鹿たれ" (Romanized: "bakatare", Meaning: "Idiots!"), "馬鹿野郎" (Romanized: "bakayarou", Meaning: "Damn fool!"), "馬鹿ばかし" (Romanized: "bakabakashi", Meaning: "Nonsense!"), "大馬鹿" (Romanized: "Oobaka", Meaning: "Big idiot!"), and "バカップル" (Romanized: "bakappuru", Meaning: "Stupid Couple" or "Sickeningly Sweet Lovebirds"). Its use can be vary greatly and, depending on the context (military, household, workplace, etc.) and style of use (harshness of tone, relative social positions, age of speakers, etc.), range in meaning from a severe reprimand to childish teasing.
It is also often used to speak about Cirno.