A "singular act" refers to an action or behavior that is unique, special, or stands out from usual activities. It is something that is done only once or rarely and holds significant importance or individuality in a specific context. Full definition
In 2013, Glynn performed The Myth of Singularity (After Rodin), in which she explored, along with a group of sculptors, the process of replication, recombination and shifts in material and scale often used by Rodin in producing works later regarded as singular acts of brilliance. (blog.calarts.edu)
They wind up on the literal trash heap of the galaxy, a planet called Sakaar, run by a grandiose hedonist known as the Grandmaster (Jeff Goldblum, whose singular acting style is a perfect fit for the movie's weirdness). (movieink.net)
«The PDP made the supreme sacrifice to make Nigeria one and ensured that our indivisibility as a people and as a country was not compromised and that was why our presidential candidate in the 2015 election conceded defeat to President Muhammadu Buhari which singular act contrary to the expectation of pessimists that Nigeria remained one country.» (punchng.com)