綻びる

ほころびる · hokorobiru · JLPT N1 · verb-ichidan

to come apart at the seams

🧵 糸 (thread) radical: a seam giving way, and also a face splitting into a broad grin

Both meanings share one idea: something tightly joined gives way and opens up. The 糸 (thread) radical marks the stitched seam that starts to fray.