WordWeb Online

1. Important in effect or meaning
   "a significant change in tax laws"; "significant details"; "statistically significant";
   - important
    
2. Of considerable importance, size, or worth
   "won by a significant margin";
   - substantial
    
3. (statistics) 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"
    
4. Rich in significance or implication
   "a significant silence";
   - meaning, pregnant

See also: considerable, earthshaking, earth-shattering [informal], epochal, epoch-making, evidential, evidentiary, fundamental, important, large, meaningful, momentous, monumental, notable, noteworthy, of import, operative, portentous, probative, probatory, prodigious, profound, remarkable, significance, world-shaking, world-shattering

Antonym: nonsignificant

Encyclopedia: Significant