As a trans person, I assure you that crossdressing is, in fact, queer. It doesn't necessarily make a person trans, but it's not straight behavior.
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As a person that likes to know what words mean, I can assure, you, queer does not include crossdressing. You got it backwards. While self identified queer people might engage in an activity they call crossdressing*, this does not make crossdressing queer .
If you disagree, I suggest you educate the nitpickers at wikipedia. Because they define queer as an umbrella term for people who are not heterosexual or are not cisgender. And there is not a single word about crossdressing on that page.
And the page for cross-dressing reads The term "cross-dressing" refers to an action or a behavior, without attributing or implying any specific causes or motives for that behavior.
And if you do, that is prejudice on your part. Might wanna think about that.
Also, there is no such thing as straight or unstraight behaviour. Every person is capable of feeling all feelings and doing all activities for fun that are usually attributed to the other gender or the other sexualities. With the trivial exceptions that are word defining.
* I am not convinced that this activity can be called crossdressing for a trans or a queer person. They want to reaffirm their felt gender, so it is not crossdressing to them. What would crossdressing for a mtf look like? Wearing male clothes again?