Deeply involved in something; oversupplied or overwhelmed with something.
Examples:
- I'm up to my ears in work.
- He's in up to his eyes with the in-laws.
Origin: First recorded in 1839; variants with eyes (1778), eyeballs (1911), neck (1856), wazoo (1981)
Synonyms: up to one, , , s eyeballs, up to one, , , s wazoo