1. to say no to; to reject or refuse
2. to speak against; to express doubt or disapproval of

Examples

• She refused to naysay his ambitious plans, even though she had doubts.
• The committee will not naysay the proposal without hearing all the evidence.
• Critics naysaid the new technology, claiming it would never catch on.
• Don't naysay every idea just because it's different from what we've always done.
• He tends to naysay anything that requires change or innovation.
• The board naysaid the merger proposal at yesterday's meeting.