Neither of the two is slang, really.
is an informal word for []{}. It should be found in every dictionary.
is a regular dictionary word meaning "dull", "stupid", etc. Perhaps the katakana part fooled you. That is just to give the word a slangy look and feel.
**** and **** are just the continuative forms of **** and **** , respectively. The sentence uses **three** adjectives in a row, thus the first two must be put in the continuative form.
> **_"It/He was a big, stupid and easy-to-use jump stand."_**