In a sexual manner: erotically.
"The dancer moved sexually across the stage, captivating the audience with her fluid and erotic performance."
In plain English: Sexually means relating to sexual acts, desires, or reproduction.
"The advertisement was rejected because it contained sexually explicit images that were considered inappropriate for children."
The word sexually comes from combining the adjective sexual with the suffix -ly to form an adverb. This construction simply adds a "-ly" ending to indicate that something is done in a sexual manner.