Formal:
"centi-bit" (cBTC) / "milli-bit" (mBTC) / "micro-bit" (µBTC) / "satoshi" (sBTC)

Slang:
"ceebits" (cBTC) / "embits" (mBTC) / "youbits" (µBTC) / "satoshi" (sBTC)

But I think the cBTC one is unnecessary. Also, it'd be easier for µBTC to be written as uBTC.

All these denominations could collectively be called "bits". "How many bits would that be? 20 youbits. Here, thanks."