It expresses a feeling of being overwhelmed, surprised, or unable to find the right words to respond.
Here are some examples of how it might be used:
* "Nakita mo ba yung performance niya? Wala ako masabi!" (Did you see their performance? I'm speechless!)
* "Grabe ang ganda ng regalo mo! Wala ako masabi." (Wow, your gift is so beautiful! I'm speechless.)
* "Napakasama ng nangyari. Wala ako masabi." (What happened is terrible. I have no words.)
Essentially, "wala ako masabi" is a way of acknowledging that something is so impactful or significant that words fail to express the speaker's feelings.