fool's gold noun

Iron pyrites

fool's mate noun

In chess, the simplest of the checkmates (in two moves by each player)

fool's paradise noun

A state of happiness based on fictitious hopes or expectations

fool's parsley noun

A poisonous umbelliferous plant (Aethusa cynapium) that a great enough fool might take for parsley

All Fools' Day see under all

fool about or around

1. To waste time
2. To mess about
3. To trifle with someone's affections, or to be unfaithful to them with a reckless attitude
4. To have sex, or indulge in sexual frolicking

fool away

To squander to no purpose or profit

fool with

To meddle with officiously, irresponsibly or thoughtlessly

make a fool of

1. To cause (someone) to look ridiculous or stupid
2. To humiliate or dupe
3. To disappoint

nobody's fool

A sensible, shrewd person

play or act the fool

1. To behave like a fool
2. To be reckless or foolish
3. To be exuberantly comical or high-spirited

pyrites /pī- or pi-rīˈtēz/

1. A brassy yellow mineral, iron disulphide, crystallizing in the cubic system, occurring in octahedra, pyritohedra, etc (also called pyrite /pīˈrīt/, iron pyrīˈtēs, fool's gold)
2. Extended to a large class of mineral sulphides and arsenides

pyritic /pir-itˈik or pīr-itˈik/ or pyritˈical adjective

pyritifˈerous adjective

pyrˈitize or pyrˈitise transitive verb

To convert into, or replace by, pyrites

pyritohēˈdral adjective

pyritohēˈdron noun (pl pyritohēˈdra)

A pentagonal dodecahedron

pyrˈitous adjective

arsenical pyrites

Mispickel

cockscomb pyrites or spear pyrites

A twinned form of marcasite

copper pyrites

Sulphide of copper and iron, chalcopyrite, a mineral very similar to iron pyrites

magnetic pyrites

Pyrrhotite