This is the 2393rd most frequent Japanese word.
チン
"チン" (chin) is an onomatopoeia used to mimic the sound of a microwave beeping or a small bell ringing.
チン is mimetic and refers to the sound of a microwave finishing its cycle.
電子レンジでご飯をチンしてください。
Please heat the rice in the microwave.
チン is used here as an informal way to describe heating food, specifically in a microwave, derived from the sound effect.
お母さんがチンしたピザ、とてもおいしかった。
The pizza heated by mom was very delicious.
チン refers directly to the onomatopoeic sound made by the bell.