1To cook grains such as rice by adding water and heating them until done; most commonly used in the phrase 'ご飯を炊く' (to cook rice).
毎朝、父がご飯を炊いてくれる。
Every morning my father cooks rice for us.
炊飯器で白米を炊くのに40分くらいかかる。
It takes about 40 minutes to cook white rice in a rice cooker.
炊きたてのご飯の匂いが台所いっぱいに広がった。
The smell of freshly cooked rice filled the kitchen.
今夜は多めにご飯を炊いておこう。
Let's cook a bit extra rice tonight.
2In Kansai dialect, a broader word for simmering or stewing vegetables, fish, etc. in a seasoned broth — roughly equivalent to '煮る'.
大阪の実家では、大根を甘辛く炊いた煮物がよく食卓に出る。
At my parents' house in Osaka, daikon simmered in a sweet-savory broth often appears on the table.
おばあちゃんが小芋を優しい味で炊いてくれた。
My grandmother simmered the taro in a mild-flavored broth for us.
3Internet slang meaning 'to get angry' or 'to snap' — a figurative, casual usage unrelated to cooking.
その一言で完全に炊いた。
That one comment completely set me off.