Although usually meaning a small piece of excrement attached to the hairs of your arse, sometimes known as a Clingon, it can also mean someone who is a minor, smelly, unpleasant nuisance that is sometimes difficult to get rid of.
The fircle is a square-like shape, but with rounded edges. It can also be described as a circle with sides. A fircle is very similar, but not the same as, a squircle.
The formula for calculating the perimeter of a fircle whose four sides have length 'L' is
P = 4L - (8-2π)r
Firkle through your bag to find your keys.
I was firkling through that drawer and I found my penknife.
The pig was firkling through the fallen leaves picking up acorns.