This is the 185th most frequent Lithuanian word.
automobilių
"Automobilių" means "of cars" or "cars'" (possessive form in Lithuanian).
Genitive plural is applied here to signify 'the documents of the cars'.
Apsaugos darbuotojai tikrina automobilių dokumentus.
Security guards are checking the cars' documents.
Genitive plural indicates the engines belong to the cars.
Automobilių varikliai buvo įjungti.
The engines of the cars were running.
Genitive plural is used to indicate possession or relation, here meaning 'of cars'.