spark plug
"spark-plug" is a 9-letter English headword indexed on PlainSpell.
The verdict
“spark plug” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.
- Unranked
- below top-frequency English
- 10
- letters
According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - The part of some internal combustion engines which forms a high-voltage electric spark which ignites the fuel-air mixture to begin the power stroke. (Petrol engines have spark plugs. Diesel engines...
Corpus desk
Index EN-spark-plug · spark plug · English
spark plug · unranked · 0 variants · 0 confusables
- FREQ-UNRANKED Unranked
- LEN-MEGA 10 letters
- VOW-2 2 vowels
- CONFUS-0 No pairs
- VAR-0 0 variants
- BOOK-THIN "S" thin
- PHOTO-UNK Peer pending
Read with this headword: Spelling guide for this pattern
Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.
| Property | Value |
|---|---|
| Headword | spark plug |
| Language | English |
| Part of speech | Noun |
| Letters | 10 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Long-tail rank of “spark plug” in English
Rare enough to double-check
spark plug is uncommon English outside the top frequency list, classed as anoun. Rarity is why readers land here mid-draft. 3 senses are on record.
The misspelling generator found no plausible variants for spark plug, which points to an orthography that plays by predictable English rules. This headword has no recorded confusable partner, since its spelling is unusual enough that it doesn't cluster with a lookalike.
No documented word history exists for this headword, so its spelling pattern is best understood through pronunciation rather than a traceable origin. The correct English form is spark plug, spelled S-P-A-R-K- -P-L-U-G.
Definition
- 1The part of some internal combustion engines which forms a high-voltage electric spark which ignites the fuel-air mixture to begin the power stroke. (Petrol engines have spark plugs. Diesel engines do not have them because the heat from their high compression ratios supplies the ignition.)
- 2Someone who is a driving force in new endeavours.
- 3A rod (for cylindrical secondaries) or sphere (for spherical secondaries) of fissile material at the center of the secondary of a multistage thermonuclear weapon, which undergoes nuclear fission when compressed to supercriticality by the imploding secondary, helping to raise the secondary to the pressures and temperatures necessary to ignite nuclear fusion in the secondary's fusion fuel.
Recorded use
Wiktionary examplesThese source excerpts show how spark plug appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.
In the 21st century, it is not unusual for a set of spark plugs to last a decade or longer; gone are the days when changing the plugs annually was common.
With all engines using spark plugs it is comparatively easy to ascertain whether the ignition system is working properly.
This word in other languages
Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA). See the methodology for how each field is sourced and updated.