Yeah, cavitation. Capitation would be...I dunno, putting a head on something as the opposite of decapitation?
I don't know if the pumps we're likely to use would have any cavitation problems, but I did find that the powerhead I used on my 404 was noisier when sucking through a restriction than blowing. Same for a couple laguna pond pumps I have. Possibly is cavitation, it's hard to tell. Sounded more like the impeller rattling.