Majig
A substitute word for anything one has no words for, or have forgotten. It could be used both formal and informal situations. This word can be used in any context possible. It could be used in any form of grammar. A very versatile word.
The farmer is majigging his crops, I have no idea what he is doing. But it makes the crops grow nevertheless.
A mechanic used his majig to majig the majig. (someone who has no knowledge and words of mechanics is attempting to describe what a mechanic did to something)