Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. Here's a refresher to help you remember the き portion of this word:
Something is snapping. Turns out that something is your arm. Your arm is a 木 (き) that grew out of you one day. "What's this ki doing here?" you ask. Then it suddenly breaks in half! "OW OW OW! My ki! It's been cut!!"
The tape was cut.
I feel lonely when I hear the sound of the phone being cut off.
The thread snapped.