A verb meaning to begin eating or to start to eat (close in meaning to 'to start eating').
夕飯を食べ掛けたところに電話がかかってきた。
Just as I started dinner, the phone rang.
彼は忙しくて、スープを食べ掛けのまま席を立った。
He was busy and left his seat with his soup half-eaten.
お菓子を食べ掛けにしておくのは衛生的に良くない。
Leaving snacks half-eaten is not hygienic.