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)