play fast and loose
idiom

- to treat someone or something in a careless way

(Macmillan Dictionary)

---
According to the Phrase Finder, the expression "play fast and loose" derives from an old deception or cheating game in which something that appears stuck (fast) easily becomes loose. In James Halliwell's 18th century dictionary that covered a wide range of archaic and provincial words, obsolete phrases, proverbs and ancient customs from the 14th century, he describes a popular game played at fairs:

"Fast-and-loose, a cheating game played with a stick and a belt or string, so arranged that a spectator would think he could make the latter fast by placing a stick through its intricate folds, whereas the operator could detach it at once."

There is additional evidence that the expression has been in use for many centuries. Shakespeare used it in King John from 1595:

And shall these hands, so lately purged of blood,
So newly joined in love, so strong in both,
Unyoke (separate) this seizure and this kind regret (greeting)?
Play fast and loose with faith? So jest with heaven.

Play is one of the most versatile words in English and is used a wide variety of expressions. Following is just a small sample:

- play with fire = to do something dangerous (If you borrow his laptop without asking you are playing with fire)

- play the fool = to act silly for the amusement of others (He likes to play the fool)

- play by ear = to deal with a situation as it develops (Let's just play it by ear and see what happens)

---
SYNONYMS

(intransitive verbs/adjectives)

irresponsible, reckless, uncontrolled, undisciplined, unrestrained

---
SMUGGLE OWAD into today's conversation

"He is known to play fast and loose with the facts."