It's a slang similar to the american "wut up", it's often used to say "Hello" or "how are you".

Contraction of good day.

Informal Thursday afternoon drinks with co-workers. Abbreviation of "donderdag" (Thursday), "middag" (afternoon) and "borrel" (informal drinks). Used to be on Friday (vrijmibo) but since more people are working form home on Fridays, it is now often moved to Thursday.

An informal meetup, usually involving alcoholic drinks and snacks, held on Friday afternoon (typically with one's colleagues or friends) at the end of the workweek. Shortened from vrijdagmiddagborrel, taking the initial syllables of its constituent words vrijdagmiddag (“Friday afternoon”) and borrel (“informal meetup or reception involving alcoholic drinks”).

A short form of McDonald's.