1. in a way that sounds empty or echoing, as if coming from a hollow space
2. in a way that lacks sincerity, substance, or conviction

Examples

• The wind whistled hollowly through the abandoned building.
• He laughed hollowly, without any real joy or warmth.
• She spoke hollowly about her achievements, as if they meant nothing to her.
• The promise rang hollowly in their ears after so many broken commitments.
• His voice echoed hollowly down the empty corridor.
• The victory felt hollowly won, tainted by unfair tactics.