Commonly used as a curse-word.
It's a word from SEA (South-East Asia).
Somehow, it could mean "bad luck" or something along the lines of "hardship".
But commonly used like when you say "Shit!".
(But it doesn't mean "Poo")
It may also be used to address someone rudely.
(Which you could
translate to "Shithead")
Other variants of this are:
-"Sialan" (Another
way to say "Sial")
-"Be(r)sialan" (Meaning:
Being a shit or shithead)