What is a "splicing variant"?

You're wrong. It's not a matter of expression. However, the splicing methods of pre-mRNA produced by eukaryotic gene expression are different, and the mature mRNA produced is also different, so the final protein is also different. For example, the pre-mRNA has exon 1- intron 1- exon 2- exon 3. After processing, the mature mRNA can be exon 1- exon 2- exon 3, exon 1- exon 2, exon 2- exon 3 and exon 3. This series of mRNA is called splicing variant.