thin blue line

noun

"thin-blue-line" is a 12-letter English headword indexed on PlainSpell.

The verdict

“thin blue line” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.

Unranked
below top-frequency English
14
letters

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - The police.

Corpus desk

Index EN-thin-blue-line · thin blue line · English

thin blue line · unranked · 0 variants · 0 confusables

  • FREQ-UNRANKED Unranked
  • LEN-MEGA 14 letters
  • VOW-5 5 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-THIN "T" 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.

Key facts for thin blue line
PropertyValue
Headwordthin blue line
LanguageEnglish
Part of speechNoun
Letters14
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “thin blue line” in English

thin blue lineranks outside the top 100,000 English headwords, in the long tail of specialist, archaic, or seldom-used vocabulary, exactly the territory where a reader stops mid-sentence to double-check spelling.

Beyond rank #100,000. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

thin blue line is uncommon English outside the top frequency list, classed as anoun. Rarity is why readers land here mid-draft. 2 senses are on record.

Zero misspellings are on record for thin blue line in our index, and the word's spelling is regular enough that our generator found nothing worth flagging. No confusable counterpart is on file for this word, suggesting its spelling stands apart enough that readers rarely confuse it with something else.

Etymologically, the entry records: By analogy with Thin Red Line. “Blue” refers to the color of the uniforms of many police departments. The correct English form is thin blue line, spelled T-H-I-N- -B-L-U-E- -L-I-N-E.

Definition

  1. 1
    The police.
  2. 2
    A flag or symbol representing the police, commonly associated with the blue lives matter movement.

Recorded use

Wiktionary examples

These source excerpts show how thin blue line appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. Crime wave overwhelms thin blue line [title]
  2. It followed dire warnings from the police staff associations that the possible loss of up to 40,000 police jobs would mean “Christmas coming early” for criminals, and the “thin blue line” left too stretched to cope with the inevitable risk of social and industrial unrest.

Etymology

By analogy with Thin Red Line. “Blue” refers to the color of the uniforms of many police departments.

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.

Frequently Asked Questions

How do you spell "thin blue line"?
"thin blue line" is spelled T-H-I-N- -B-L-U-E- -L-I-N-E.
What does "thin blue line" mean?
As a noun, "thin blue line" means: The police.
What is the origin of the word "thin blue line"?
By analogy with Thin Red Line. “Blue” refers to the color of the uniforms of many police departments. See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list