Answer:
Thomas and Leanna are engaging in gender non-conformity.
Step-by-step explanation:
As the name states, gender non-conforming refers to not accepting gender roles established by society.
Gender roles are specific behaviors, responsibilities and values attributed to each gender. This means a girl would be expected to dance ballet while a boy is expected to play football or not show his feelings too much, for example.
In this case, both Thomas and Leanna have chosen to not conform to their gender roles, doing what they want instead such as Thomas wearing a dress and Leanna having a buzzcut and swearing a lot.