godan verb (-mu), intransitive verb
Physical sense: something presses or cuts into a surface or flesh, often causing discomfort or a mark. Common with ropes, straps, fingernails, or tight clothing.
重い荷物で肩にひもが食い込んだ。
The strap bit into my shoulder from the heavy luggage.
爪が
I clenched my fist so hard that my nails dug into my palm.
godan verb (-mu), intransitive verb
eat into; encroach; make inroads; erode
Figurative use: something gradually reduces or takes over a resource, market, position, or time. Often used in business, sports, and scheduling contexts.
新興企業が大手のシェアに食い込んでいる。
Startups are eating into the major companies' market share.
残業で自由時間がどんどん食い込まれた。
Overtime work has been eating into my free time more and more.
godan verb (-mu), intransitive verb
ride up; get wedged (underwear)
Vulgar/casual: underwear becomes uncomfortably wedged between the buttocks. Often used in the phrase パンツが食い込む.
このパンツ、すぐ食い込むから嫌だ。
I hate these underpants; they ride up right away.