This is the 5069th most frequent Turkish word.
haftaki
"Haftaki" means "in the week" or "of the week" in English.
In this sentence, 'haftaki' is used to describe 'toplantı' (meeting) and indicates that the meeting occurred in 'geçen hafta' (last week).
Geçen haftaki toplantı çok verimli geçti.
Last week's meeting was very productive.
Here, 'haftaki' qualifies 'sınava' (exam) and specifies that the exam belongs to 'önümüzdeki hafta' (the upcoming week).
Önümüzdeki haftaki sınava çalışmaya başladım.
I started preparing for the exam of the upcoming week.
In this context, 'haftaki' is used to modify 'hava durumu' (weather) and denotes that the described weather conditions pertain to 'bu hafta' (this week).