To persuade someone (Usually a parent) to let you get/do something they wouldn't normally allow. Often associated with cuteness.
"I'm going to be trying to squiffle my Dad into letting us get a cat over the next few days"
"Hey, guess what?! I got a pony!!"
"Wow, how'd you manage that?!"
"Well.. lets just say that a certain amount of squiffling went on over the holidays.."
To leave less than a full portion of something in a misguided effort to be polite.
Sometimes this is an attempt to avoid guilt for consuming the last portion. Most commonly used in reference to food, but can be used with supplies and materials.
"My sister squiffled the cookies."
(She left just one in the package, rather than simply finishing the package.)
The combined act of shuffling over and squishing together to make room for someone to sit down.
"If you squiffle a bit I'm sure we can fit four on the sofa."