Prodigious
Part of speech: adjective
Definition: Very big in size or quantity; gigantic; colossal; huge.
Significant
Part of speech: adjective
Definition: Signifying something; carrying meaning.Having a covert or hidden meaningHaving a noticeable or major effect; notableReasonably large in number or amountHaving a low probability of occurring by chance (for example, having high correlation and thus likely to be related).
Example sentence: America needs a new generation of leaders to address the big issues facing the country: alleviating the middle class squeeze and promoting economic opportunity, confronting the significant national security challenges threatening the safety of our people, and reforming the culture of Washington, D.C.