1.
to become corrupt
The neighbors' son became corrupt; he's started to smoke. وِلْدْ الجِيرَانْ فْسِدْ، وَلَّا يِتْكَيِّفْ wild jiyran fsid, walla yitkayyif
2.
to decompose, go bad, go rotten
Milk goes bad if you don't put it in the fridge. لحليب فسد كيف ما تحطّش فالفريجيدار l7lyb fsd kyf m t7ttch flfryjydr