Under-pinning means the foundation or the base of something, and its antonyms are detachment, isolation, and separation. Detachment refers to the act of separating oneself emotionally from others or something. Isolation is the state of being disconnected or separated from others or a group. Separation means the act of dividing or breaking the bond between two or more entities. These antonyms highlight the opposite meaning of under-pinning. While under-pinning refers to the support or foundation that holds something together, detachment, isolation, and separation indicate separation or removing oneself from others or something. In essence, these antonyms show the different directions a thing or a person can go - towards connection and support or towards disconnection and detachment.