Definition 1 of 1
Literally translated: "Oiling your mustache in anticipation of the jackfruit tree bearing fruit". It means "Don't get ahead of yourself." An American equivalent might be, "Don't count your chickens before they're hatched."
The Bangladeshi version makes the assumptions that:
a) You love jackfruit (which is milder than durian but if even slightly overripe smells like diarrhea),
b) You have a mustache that's thick enough that it would be a hindrance to eating the juicy and sticky jackfruit,
c) You oil the mustache before you eat the jackfruit so that the remnant stink (which can get pretty intense) doesn't fuck with your luxurious facial hair, and
d) You are so excited by the idea of eating jackfruit that you oil your mustache in anticipation of this glorious event.