This is not a word that can be found in standard dictionaries.
It’s a Tagalog transliteration of the English phrase “best friend.”
Bespren kita.
You are my best friend.
Mag-bespren tayo.
You and I are best friends.
Mag-bespren kami.
We (not including you) are best friends.
The native Tagalog equivalent is matalik na kaibigan (“close friend”).