Symbolism of Impermanence: The skull is a potent symbol of impermanence (anicca) and the transient nature of life. It serves as a reminder of mortality and the inevitability of death, encouraging practitioners to contemplate the impermanent nature of all phenomena.

Symbol of Wisdom (Kapala): In certain Buddhist traditions, particularly in Vajrayana (Tibetan Buddhism), the skull can be specifically referred to as a "kapala," which translates to "skull cup." A kapala is a ritual implement made from a real human skull used in certain tantric practices. It symbolizes the transformation of negative emotions into wisdom and the transcendence of ego-based attachments.
Use in Tantric Rituals: Within Vajrayana Buddhism, the kapala plays a ritualistic role in ceremonies known as Chod (or "cutting through ego"), where practitioners visualize offering their own body as a feast to spiritual beings. This practice symbolizes the practitioner's fearless engagement with impermanence and the ultimate reality of emptiness.

Artistic Symbolism: In Buddhist art, skulls can be depicted as adornments or decorative elements on wrathful deities or protectors, symbolizing their transcendence over death and ego. Skulls may also be featured in thangka paintings, sculptures, and ritual objects as a potent symbol of transformation and spiritual realization.

Cultural Context: The significance of the skull in Buddhist culture reflects broader themes of Buddhist philosophy, including the Four Noble Truths and the practice of mindfulness of death. Meditating on the image of a skull is a contemplative practice aimed at deepening insight into the nature of existence.

Ethical Considerations: It's important to note that in Buddhist contexts, the use of actual human remains (such as kapalas) in rituals is subject to ethical guidelines and cultural sensitivities. Many modern practitioners use symbolic representations of skulls or other ritual objects to engage with the teachings of impermanence and wisdom.

In summary, the Buddhist skull symbolizes profound spiritual themes related to impermanence, wisdom, and transformation within Buddhist philosophy and practice. Its symbolism invites practitioners to contemplate the nature of existence and the path towards awakening, emphasizing the impermanent and interconnected nature of all phenomena.