If you've ever seen The Da Vinci Code (not the best source of trustworthy information, we know), you'll have heard that, historically, some abstract shapes have tended to be associated with masculinity and some, like that upside-down triangle that Robert Langdon is always going on about, have tended to be associated with femininity.
Abstract representations of masculinity and femininity are all over the place—so much so that we learn to associate certain shapes and forms with masculine energy and female energy without ever thinking too much about it. Tall, narrow skyscrapers—like the Empire State Building, or the apartment complex that Joanna and Janet enter when they attend the party on Riverside Drive—are examples of masculine architectural form. (Insert joke about penis envy here.) Rounder, more curved enclosures—like the caves that many Whileawayans inhabit—are typically associated with femininity. In some feminist writings, like the literary criticism of Sandra M. Gilbert and Susan Gubar, caves are even read as symbols of the womb.
On top of its skyscrapers and caves, The Female Man is jam-packed with other examples of this kind of symbolism. Take, for example, one of the sculptures of the female Whileawayan God: an abstract piece made up of "three silver hoops welded to a silver cube" (3.8.1). Or, think about the joke that Joanna Russ is making when she writes that the Whileawayan symbol representing male genitalia ("the sideways eight that means infinity" with "straight line" running "down from the middle") is also the Whileawayan "mathematical symbol for self-contradiction" (5.12.4).
One of the neatest examples of abstract symbolism we find in the novel is Jael's home. We aren't told much about it, but Jael calls the house her "old round lollipop-on-a-stick," and it's clear that it's at least a little bit convex (8.9.1). Rounded architecture doesn't necessarily make for a feminine vibe, but certain elements of Jael's description definitely suggest that this is a female space. The biggie is that she compares it to Baba Yaga's hut (8.9.1), an allusion that prompts us to associate both the house and Jael herself with the ambiguous old crone who appears in Slavic folklore.