to chew, to bite
齩 centers on using the teeth to break down or grip something: chewing food or biting down.
齩 combines 齒 (teeth) with 交, which likely contributes the sound and may suggest the action of teeth coming together or crossing in a bite.
The left side 齒 shows a mouth full of teeth, and the right side 交 looks like crossed lines. Picture teeth crossing over food as they chew and bite.
For コウ, imagine a cow chewing its cud: cow -> コウ, and the cow's teeth are busy biting and grinding.