"What Was That" is a song by New Zealand singer Lorde, released on April 24, 2025, as the lead single from her fourth studio album, Virgin. The song was co-written and produced by Lorde along with Jim-E Stack and Daniel Nigro. It is an electropop, synth-pop, and dance track inspired by the drum sound in Radiohead’s 2007 song "Reckoner." The lyrics reflect on a past relationship, touching on memories, emotional aftermath, and personal growth. The song's narrative includes references to experiences like taking MDMA and sharing intense moments in a past relationship. It also deals with themes of heartbreak and moving on, with an introspective and nostalgic tone that recalls some of Lorde's earlier work, particularly her album "Melodrama." "What Was That" was promoted with a surprise event in New York City's Washington Square Park, which drew a large crowd but was shut down by the police due to lack of permits. The music video features Lorde walking through parts of New York City, culminating in a dance performance surrounded by fans. Lorde revealed that the song originated during a difficult breakup in late 2023, capturing the emotional turmoil and grief she experienced, making the track a raw expression of rebirth and recovery. Overall, "What Was That" marks a return to a more electronic and emotionally complex sound for Lorde, garnering positive reviews and chart success in several countries. The song's production, lyrics, and promotional rollout highlight a significant moment in Lorde's artistic journey and personal life.