The adjective simpatico (sympatico is a misspelling) has a few definitions in English, including (1) likeable, (2) (of two or more people) having personal or intellectual affinity, (3) tending to get along with others, and (4) closely associated (with). It also works as a noun for a simpatico feeling or a simpatico relationship.
Simpatico is Spanish and Italian for sympathetic (the Spanish word has an accent over the a), and the English simpatico, which entered the language in the late 19th century, is roughly synonymous with sympathetic without bearing that word’s baggage. Of course, the Spanish and Italian words have plenty of baggage of their own, but this doesn’t carry over into the English use of the word, except in writing about Italy or Spanish-speaking countries.
In Spanish and Italian, simpatico becomes simpatica when modifying feminine nouns. Although nouns in English are ungendered, simpatica occasionally appears in reference to females. These instances are rare, though, and in general simpatico is used without regard to the gender of what it describes.
Simpatico can have a colloquial ring in English, so some might consider it out of place in formal writing.
The Oprahfication of America has spawned a new kind of icon: the simpatico celebrity, rich and famous but also down-to-earth. [Advocate]
Trading and meshing phrases like champion relay runners, they made a simpatico team in tandem with Bicket and the CSO strings. [Chicago Tribune]
If he was not always simpatico with the hippie ethos, the Acid Tests, at least, seemed to have been tailor-made for him. [Neal Cassady: The Fast Life of a Beat Hero, David Sandison and Graham Vickers)]
The Scientology-loving 70-year-old Corea and the precise, porkier 69-year old Burton appear to be totally simpatico, complementing each other perfectly. [Independent]
They’re still simpatico enough that Hannah promises not to out him to the authorities, but when they kiss during a prison visit, she draws blood. [Seattle Post-Intelligencer]
She and Dana were simpatica, and Dana desperately needed a knowledgeable partner. [Don't Mess with Texans, Peggy Nicholson]