This is a Filipino slang word that almost always appears as part of the phrase May topak.
Has something strange or crazy (about him).
May topak sa ulo.
Has a screw loose in the head.
May topak siya sa utak.
He has a screw loose in his brain.
Can also be a noun.
His/Her mental illness is serious.
Matindi ang topak niya.
His/Her mental illness is severe.
Related Tagalog expressions:
“Broken head.” = crazy
Has soy sauce (in the brain).