For "full of significance or importance":
* Meaningless: Lacking significance or importance.
* Pointless: Having no purpose or value.
* Futile: Ineffective or useless.
* Superficial: Concerned with appearances rather than substance.
* Frivolous: Lacking seriousness or importance.
For "having a clear purpose or intention":
* Ambiguous: Unclear or open to multiple interpretations.
* Vague: Not clearly defined or expressed.
* Abstract: Not concrete or specific.
* Indecipherable: Impossible to understand or interpret.
For "evoking strong emotion or feeling":
* Unmoving: Not arousing any emotion.
* Indifferent: Showing no interest or concern.
* Cold: Lacking warmth or feeling.
* Uninspiring: Failing to motivate or stimulate.
The best opposite for "meaningful" will depend on the specific context and what aspect of meaningfulness you want to contrast.