u got the concept right but multis to me are syllables that not only rhyme but match in syllable count
I see a lot of people on the site (both newbs & vets) not  knowin what multis are & identifyin them wrong... so i thought id  drop this guide usin some good examples i used on the site (No, it aint  recyclin lol)
--------------------------------------------------------------------------------
bla bla 
dikk bla bla 
kick bla bla 
thick
bla bla 
quick bla bla 
stick bla bla 
trick
^ A lot of people think that is a multi because you rhyme the same sound multiple times, but that 
IS NOT a multi...
--------------------------------------------------------------------------------
Multi means multi-syllable rhymin... 
This is basically a link up of words with the same amount of total  syllables that are used more than once in a bar & sound similar
For example:
Stabbin this kid with used needles, providin infections-that-maim 
Might be good, but ill smear ya rep worse than an election-campaign 
 
They sound the same and have the same syllable count... syllables are just the amount of sections you cut the words down into...
 
In-fec-tions-that-maim - 5 Syllables
E-lec-tion-cam-paign - 5 Syllables
 
That keeps the flow on point and gives your multi a hard hittin edge
If your multis dont have the same syllable count, it makes your flow sound off and they will not be anywhere near as effective
 
You can use multis in sets of threes or more as you get better with them, for example:
Ill haunt-and-maim-ya, youll want-a-saviour 
Coz ill put you in pain for weeks like a torture-chamber
Haunt-and-maim-ya - 4 syllables
Want-a-sav-iour - 4 syllables
Tor-ture-cham-ber - 4 syllables
You might even wanna try usin 2 sets of multis, like this:
Your flows-so-hopeless-kid, for real im rapin-your-script-son
Leave your bones-all-broken-bytch with this blazin-enscription
Flows-so-hope-less-kid - 5 Syllables (Set 1)
Bones-all-bro-ken-bytch - 5 Syllables (Set 1)
Ra-pin-your-script-son - 5 Syllables (Set 2)
Bla-zin-en-scrip-tion - 5 Syllables (Set 2)
and here is a rhyme dictionary called rhyme zone that will help you with what rhymes and what don't rhymes
RhymeZone rhyming dictionary and thesaurus