Too many alien kisses on your mouth Have left their careless and ironic mark In shreds of disillusionment!—enough To nullify and quench a vital spark.
Why should I give you then my living lips? With all my singing heart for ecstacy Upon them—bearing dreams you could not share That shall one day wing to reality!
A woman turns down a lover, and "Rebellion" is her explanation. The speaker looks at the person she addresses and sees someone who has been kissed too often, and carelessly. Those earlier kisses have left "shreds of disillusionment," as though the mouth itself has gone dull and stopped being capable of real feeling. So she asks a pointed question: why should she offer her own lips to that?
What makes her refusal more than a rejection is how much she thinks her kiss is worth. Her lips carry her "singing heart" and "dreams you could not share," and she expects those dreams to "wing to reality" someday, just not with this person. The tone is proud and a little scornful, but also hopeful. She isn't giving up on love so much as holding out for something better. The title fits: she is rebelling against settling, and the poem's mood is defiant, confident, and sharply self-respecting.