noun

the larva of an insect, especially a beetle.

my onions are ruined by small grubs eating the roots

larva,maggot,caterpillar

verb

dig or poke about in soil.

the damage done to pastures by badgers grubbing for worms

dig,excavate,burrow,tunnel,poke about,poke around,scratch about,scratch around,rake through,sift through,explore,probe,delve