Shaad means happiness.
Beautifully used in this sher by Sahir Hoshiyarpuri:
Kaun kehta hai mohabbat ki zuban hoti hain
Yeh haqeeqat to nigahon se bayan hoti hain
Who says that love has a language
This truth can only be expressed through a glance, a look
Rooh ko shaad karey dil ko jo purnoor karey…
Har nazaaray mein yeh tanveer kahan hoti hain
One who brings happiness to the soul, fills the heart with light
Where can such radiance be found in every view
Shaad Ali is also an Indian film director with three films to his credit – Saathiya, Bunty aur Babli and Jhoom Barabar Jhom. He is also the son of Muzaffar Ali, who has made classic films like Umrao Jaan, Anjuman and Gaman.
urduwallahs 
Is ‘shaad-bad’ related to this word too…like in the pakistani anthem “pak sar zameen shaad baad”? and in the same formation like “zindabaad”…hmm then “shaaadbaad” is a great word, that would in effect me ‘long-be-happy’….
Aadab! – thats an interesting observation. Though it seems the word ‘bād’ in the anthem lines “pāk sarzamīn shād bād, kishwar-e-hasīn shād bād” refers to a shorter usage of the word ‘abād’ which means bountiful. A translation of these two lines would be something like “Blessed be the sacred land, Happy be the bounteous realm”. Shaad here is also used as happy or blessed.
are you sure that ‘abàd’ is the suffix and that it mean ‘bountiful’?…then how is it that ones uses it in ‘zindabaad’ and ‘murdabaad’ equally? would be interesting to know. Thanks.