This is the 941st most frequent Polish word.
otwarty
"Open"
'Otwarty' is used here as an adjective describing the state of the door, which is visibly open.
Drzwi były otwarte przez całą noc.
The door was open all night.
Here, 'otwarty' metaphorically describes a mental state of being receptive to new ideas and perspectives.
Mam otwarty umysł i chętnie słucham opinii innych.
I have an open mind and I am willing to listen to others' opinions.
In this case, 'otwarty' refers to the club being operational and accessible during the specified hours.