The play Top Girls by Caryl Churchill was written during the second-wave feminist period in which women aimed at gaining equal rights, particularly in the workplace. The play focuses on Marlene, a recently promoted woman in the Top Girls employment agency.
However, besides the name of the business, the title also refers to how Marlene and the other "top girls" who appear in act I—Pope Joan, Lady Nijo, Isabella Bird, Patient Griselda, and Dull Gret—gained power. They each sacrificed something, usually a child, to gain status in the world. In act III, we learn that Marlene herself sacrificed her child, Angie, to become the top girl at Top Girl employment agency.
Ultimately, the title Top Girls has various meanings. Literally, the title refers to the employment agency. But the more important meanings in the title are the larger implications of what it means to be a "top girl." First of all, the word "girl" is a bit pejorative. Men looking for jobs or who have achieved success in the world aren't called "boys." In addition, the title refers to what it takes to become a "top" woman. This is something cisgender men generally don't have to do: sacrifice their chance at being a parent.