Muayyan means inevitable, pre-determined, definite in a sense (typically used in the context of the inevitability of death).
Here is an exceptional and popular ghazal from Mirza Ghalib’s vast repertoire, that uses this lafz. This ghazal also has the famous and often cited couplet – “Hum wahaan hain jahan se humko bhi, kuch hamari khabar naheen aati”. Scroll below for an English translation.
Koi ummeed bar naheen aati
koi surat nazar naheen aati
Maut ka ek din muayyan hai,
neend kyun raat bhar naheen aati
aage aati thee haal-e-dil pe hansi
ab kisi baat par nahin aati
Jaanta hoon sawaab e taa’at u zahad
par tabiyyat idhar naheen aati
Hai kuch aisi hi baat jo chup hoon
warna kya baat kar naheen aati
Kyun na cheekhoon ke yaad karte hain
meri aawaaz gar naheen aati
Daagh-e-dil gar nazar naheen aata
boo bhi aye charagar naheen aati
Hum wahaan hain jahan se humko bhi
kuch hamari khabar naheen aati
Marte hain aarzoo mein marne ki
Maut aati hai par naheen aati
Kaaba kis moun se jaoge, Ghalib
sharm tumko magar naheen aati
No hope seems to come my way, no countenance shows itself to me
That death will come one day is inevitable, then why does sleep escape me all night?
I used to laugh at the state of my heart, now nothing brings a smile to me
Though I know the reward of religious devotion, I am not inclined in that direction
It is for these reasons that I am silent, if not, would I not speak to you?
Why should I not remember you, even if you cannot hear my cry..
You don’t see the anguish in my heart O healer, the scent of my pain eludes you
I am now at that point that even I don’t know myself (or hear of my own condition)
I die in the hope of dying, death arrives and then it doesn’t come
How will you face Mecca, Ghalib, when shame doesn’t come to you
Here is the ghazal in a wonderful rendition by Ali Zafar:
And here is a very different rendition of the ghazal, amongst many other Ghalib couplets and words, in Rahat Fateh Ali Khan’s voice: