IPA: /ˌɒksɪˈmɔːrənɪk/
KK: /ɑkˈsɪmərɒnɪk/
Relating to a figure of speech where two contradictory words or ideas are combined to create a new meaning.
The phrase 'deafening silence' is an example of an oxymoronic expression.
Oxymoronic → It is formed from "oxy-" (from Greek "oxus", meaning sharp or keen) and "moron" (from Greek "moros", meaning foolish). The word describes a figure of speech that combines contradictory terms, hence the sharpness of one idea contrasts with the foolishness of another.
Think of 'sharp' ('oxy-') ideas clashing with 'foolish' ('moron') ones — that's what makes something oxymoronic.