Comparative form of slippy: more slippy(adjective)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "slippier" in a sentence
"But they don't agree with you - they think ripping CDs is a violation, regardless of the location of the originals. your slope gets slippier by the moment."
"The slope from SPD's to inline skates is slippier than you think."
"I'll still use my Boyes for wool knitting but these are perfect for slippier yarns like the Rowan Linen Drape I'm currently knitting a sweater from."