verb/koˌmeɾse el ˈtaro/
to scratch one's head
“Consultó la hora: era demasiado pronto para cenar y estaba demasiado cansado como para seguir comiéndose el tarro en la esperanza de concebir el razonamiento favorable que volteara la tortilla.” — He checked the time - it was too early for dinner and he was too tired to carry on scratching his head waiting for the favourable reasoning to turn it around.
Synonyms: comerse la olla, devanarse los sesos
Literally, “to eat the tub”.