The action of "Nibbling", or getting/acting "Nibbly" is very similar to what is commonly known as "Tweaking". Although one does not necessarily have to be under the influence of Methamphetamine or any other stimulant, "Nibbly" behavior usually occurs with those that are high on Meth. Some meth users seem to get stuck on, or apply unneccessary attention to certain "projects" that take ultimate priority over any other matters (i.e. rewiring electronics, very detailed cleaning with items like toothbrushes, reorganizing/categorizing things, handcrafting small items such as jewelry, making things of duct tape, fixing things that weren't broken, wearing headlamps....particularly in the daytime, etc...) A person who is intently working on one of these seemingly worthless activities for an extended period of time would be "Nibbling" or acting "Nibbly. It can also be used as a verb, when describing specific items that the subject will use as "Nibbles" (i.e. flashlights, cheap jewelry, tools, cleaning producs, DVD's to alphebetize)
Nibbling: "I was Nibbling
out with my label maker last night and labeled everything in my room!"
Nibbly: "She was getting a little too Nibbly
with the tweezers, so I had to stop her before she had no eyebrows left!"