I'm so hungry! Let's get out of here and get some grub!
I'm so hungry! I could grub on just about anything right now!
the word grub can be used as a noun or a verb.
In noun form, it means food. In verb form, it means eat.
In example 1, grub is used as a noun. "Let's get out of here and get some food"
In example 2, grub on is used as a verb. "I could eat just about anything..!"