significant in WordNet English dictionary

1. important in effect or meaning
   "a significant change in tax laws"; "a significant change in the Constitution"; "a significant contribution"; "significant details"; "statistically significant"
   significant  important 
   
2. rich in significance or implication
   "a meaning look"
   meaning  pregnant  significant 
   
3. too closely correlated to be attributed to chance and therefore indicating a systematic relation
   "the interaction effect is significant at the .01 level"; "no significant difference was found"
   significant 
   
4. fairly large
   "won by a substantial margin"
   significant  substantial