ísima is a suffix in spanish that means "very very", "exceptionally", "uniquely", or "extremely". It is used to emphasize the quality of something, often in a positive way. For example, "hermosa" (beautiful) becomes "hermosísima" (exceptionally beautiful). The "a" in the end means the the word is feminine.

Here ísima represents honoring the fullness of the feminine human experience. Because it is the feminine qualities that have been policed the most in our society. We want to create a space where everybody can be ísima, where they can be their wholes selves without being judged as "too much" or "not enough".