v. 1
To harm the good reputation of (a person).
The candidate tried to discredit his opponent.
v. 2
To cause (an idea or piece of evidence) to seem false or unreliable.
The evidence would tend to discredit such a theory.
n. 1
Discrediting or disbelieving.

Related words

Forms

Plural: discredits → doubts, infamies, distrusts, opprobriums…
Past participle: discredited
e.g. discredited → disparaged, disgraced, defamed, besmirched…

or Discredit?

To discredit one is to injure his reputation, as for veracity or solvency.

J. C. Fernald, English Synonyms and Antonyms (1914)

disgrace What you did brought disgrace on the whole class.
disparage We didn't mean to disparage our contenders.
defame Sami didn't want to defame anyone.
besmirch That news will besmirch his reputation for honesty.
disprove All you need is one counterexample to disprove a theory.
falsify I will falsify a permit so that I can go camping there this weekend.

Use in printed books, per decade from 1850 to 2019.

5 letters: doubt¹, shame¹, smear¹, sully², decry², odium
6 letters: stigma², infamy³, demean², malign², defame², vilify³
7 letters: scandal², degrade², impeach², tarnish², falsify³, demerit³, blacken², obloquy³
8 letters: disgrace², contempt², distrust², denounce², reproach², dishonor³, disprove², ignominy⁴, besmirch
9 letters: disbelief³, humiliate⁴, dishonour, disparage³, disrepute³, abasement, aspersion³, disesteem
10 letters: invalidate⁴, disbelieve³, stigmatize³, opprobrium⁴, stigmatise
11 letters: degradation⁴, humiliation⁵
14 letters: ingloriousness

The small number after each word is its number of syllables (sully² = 2 syllables).