Wanted to know what is 'rakawa'

Assalam alaykum,
I am learning to recite Quran. Wanted to know what is 'rakawa' My teacher told me it is the sound of the letter running in your mouth when you say it...examples are seen, Dhal and so on...
Many Thanks
Wa alaikum assalaam wa rahmatullahi wa barakaatuh.
What your teacher told you is true.  Rikhaawah is the running of the sound due to an incomplete reliance on the articulation point.
Please see the following link for more information: