Two plus people planning to do something illegal is a conspiracy.
conspiracy
noun
con·spir·a·cy kən-ˈspir-ə-sē
pluralconspiracies
Synonyms of conspiracy
1
: the act of conspiring together
They were accused of conspiracy to commit murder.
2
a
: an agreement among conspirators
uncovered a conspiracy against the government
b
: a group of conspirators
a conspiracy made up of disgruntled aristocrats
see also conspiracy theory
conspire
verb
con·spire kən-ˈspī(-ə)r
conspired; conspiring
Synonyms of conspire
transitive verb
: plot, contrive
intransitive verb
1
a
: to join in a secret agreement to do an unlawful or wrongful act or an act which becomes unlawful as a result of the secret agreement
accused of conspiring to overthrow the government
conspired to monopolize and restrict trade
b
: scheme
2
: to act in harmony toward a common end
Circumstances conspired to defeat his efforts.
… the sun and the wind conspired to make splinters out of solid wood.
—B. J. Oliphant
