This is the 6223rd most frequent Japanese word.
ギュウギュウ
"ギュウギュウ" means packed tightly, crammed, or squeezed.
Here, 'ギュウギュウ' describes the tight and crowded condition of the train, conveying a sense of compression and lack of space.
電車がギュウギュウ詰めで座れませんでした。
The train was crowded tightly, so I couldn't find a seat.
In this sentence, 'ギュウギュウ' is used to express that the belongings are packed tightly into the suitcase, emphasizing the lack of extra space.
スーツケースにギュウギュウに荷物を詰めました。
I packed the suitcase tightly with belongings.
Here, 'ギュウギュウ' describes the tight application of force, suggesting effort or intensity in the action.