Counterfeit, spurious, bogus, fake, sham, pseudo, pinchbeck, phony are comparable when meaning not at all what it is said to be or purports to be.
Counterfeit implies that what is so qualified is an imitation of something else and usually of something finer, rarer, or more valuable and that the imitation is intended to deceive or defraud; thus, play money intended for the use of children at play is imitation but not counterfeit money; a clipped coin, though intended to defraud, is a real coin and not counterfeit; but a false banknote is both imitation and intended to deceive or defraud and is counterfeit.
Spurious designates something as false rather than true or genuine; it carries no strong implication of being an imitation; thus, a spurious painting is one that is falsely attributed to a well-known painter; spurious writings attributed to Shakespeare are those thrown out of a canon of his work; a spurious condition is one which only superficially resembles the genuine condition.
The word does not necessarily connote a fraudulent purpose; it may suggest an honest mistake, confusion, or lack of scholarship.
Bogus carries the implications of fraudulence or deceit and applies to whatever may be passed off on one or may attempt to deceive one as to its true nature.
Fake and sham are often equal to the past participial adjectives faked and shammed, both usually implying a more or less obvious imitation of something real.
But fake emphasizes the idea of a false fabrication or of fraudulent manipulation and sham stresses the thinness and obviousness of the disguise, the naïveté of the deception, or often the lack of intent to imitate exactly.
Pseudo actually means false in any way; as an adjective modifying a noun or in the combining form joined with a separate noun it frequently implies pretense rather than fraud or spuriousness rather than counterfeiting.
Pinchbeck implies a cheap, tawdry, or worthless imitation often of something precious, costly, or grand; it rarely implies an intent to deceive and is therefore closer to sham than to counterfeit.
Phony stigmatizes something which does not impose but puzzles or perplexes since it has a dubious appearance of reality.