Greasy means coated in or full of fat: the shine on it, the way it slips between your fingers. Chip paper, a pan you meant to wash last night, a keyboard somebody ate crisps over.
It goes on food that is heavy with oil, a greasy breakfast, and on hair and skin that need washing, greasy roots by Thursday. Used of a person, greasy is an insult, because a greasy manner is smarmy and false, all smiles and nothing behind them. A greasy spoon is a small cheap café that fries everything, said with real affection in Britain. Watch the spelling, since the e of grease stays put, and note that both pronunciations, GREE-see and GREE-zee, are correct. Oily is the near twin, and greasy is the dirtier of the two.
1adjectivegreasyCovered in or full of grease or oil.
“He wiped his greasy hands on a rag.”
Patterngreasy + noun (hands, food, hair) · a greasy spoon · greasy chips · grease
2adjectivehairOf hair or skin: producing too much oil.
“Her hair goes greasy two days after washing.”
3adjectivesmarmyOf a person or their manner: insincere and unpleasantly flattering.
“The greasy salesman kept calling her 'madam'.”
synonyms: smarmy, unctuous
Also accepted in games: oily
GREASEy → full of GREASE
It is grease + y: chips in a paper bag, with a see-through spot where the oil has come through.
Greasy is one of the simplest builds in the language, grease plus -y, recorded in Middle English as gresi and gressy. The -y does the same work it does in muddy, dusty and sticky: covered in the stuff, full of it. Six hundred years on, nothing about the word has changed except the spelling.
Middle English
gresi
English, today
greasy
From Middle English gresi, gressy, equivalent to grease + y.
Etymology from Wiktionary, CC BY-SA