Synonyms of the word 
NIFFY → MALODOROUS - MALODOUROUS - STINKY
niffy
- adj. (colloquial) Having a bad smell.
malodorous
- adj. Having a bad odor.
- adj. (figuratively) Highly improper.
malodourous
- adj. Alternative form of malodorous.
stinky
- adj. Having a strong, unpleasant smell; stinking.
- adj. (informal) Bad, undesirable.
If you are interested in words, visit the following sites :
- wiktionary.org/niffy For complete definition of a word
- 1word.ws/niffy to play with words, suffixs, prefixs, etc.