Authorities say the suspect was waiting for the 49-year-old victim, who lives in Harlem, in the mezzanine of the Fulton Street subway station.
They got into a verbal dispute, and when she walked away, he followed her and slashed her multiple times, according to police.
She suffered lacerations to the right side of her face and the upper right side of her back.
She was taken to Bellevue Hospital in stable condition.
The 50-year-old suspect, who was wearing a tan shirt, khaki pants and tan baseball hat, fled on foot.
Detectives know his identity and where he lives, and they are actively searching for him.
Police say the suspect, who is on parole, has prior arrests for assault in February and attempted murder in March.
Submit a tip or story idea to Eyewitness News
Ex-Brit turned Manhattan resident since 2008.