This is the 535th most frequent Polish word.
ubiegłym
"Ubiegłym" means "last" or "previous" in English, typically referring to time (e.g., last year).
Here, 'ubiegłym' is used as an adjective describing 'roku' (year), meaning 'past' or 'previous'. It agrees in case and gender with the noun it modifies.
W ubiegłym roku odwiedziliśmy Kraków.
Last year, we visited Kraków.
In this example, 'ubiegłym' modifies 'tygodniu' (week) in the locative case, indicating it is the past week.
Spotkałam ją w ubiegłym tygodniu na rynku.
I met her last week at the market.
This usage shows 'ubiegłym' describing 'miesiącu' (month) in the locative case, referring to the previous month.