What does Iqlab mean?
Rather than keeping its original noon sound, the letter is converted to a meem with ghunna, the only Tajweed rule that involves an actual letter substitution rather than merging or hiding the sound.
Tajweed Rule
Iqlab
إِقْلَاب · /ɪqˈlæːb/
Iqlab is a Tajweed rule where a noon sakinah or tanween changes into a meem sound before the letter ba.