adj. 1
Happening by chance.
They only had casual meetings.
adj. 2
Careless.
adj. 3
Happening or coming to pass without design.
adj. 4
Coming without regularity; occasional or incidental.
The purchase of donuts was just a casual expense.

Related words

Word family: casualism casually casualness casualty casualwear case
Phrases: casual ward

Choose the right word

or Casual?

We speak of a thing as casual, when it falls out or happens, as it were, by mere chance, without being prearranged or premeditated; as, a casual remark or encounter; a casual observer. An idea of the unimportant is attached to what is casual.

Webster's Revised Unabridged Dictionary (1913)

Example sentences

relaxed Tom seems a lot more relaxed when Mary isn't here.
nonchalant Matthew was acting as nonchalant as he could.
unconcerned Tom said that he thought that I seemed unconcerned.
insouciant She gave an insouciant look.
occasional Heather regenerates following occasional burning.
unintentional The company claims that the delay was unintentional.

Popularity over time

Word	1850 → 2019	Trend
casual		rising
relaxed		rising
nonchalant		rising
unconcerned		rising
insouciant		rising
occasional		steady

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

By length

3 letters: odd¹, cas¹
4 letters: easy², cool¹, airy²
5 letters: light¹, daily², loose¹
6 letters: chance¹, random², mellow²
7 letters: passing², relaxed², cursory³
8 letters: everyday³, informal³, careless²
9 letters: irregular⁴, impromptu³, unplanned², extempore, causeless, unanxious, hapchance
10 letters: unexpected⁴, occasional⁴, accidental⁴, contingent³, improvised³, incidental⁴, unintended⁴, unforeseen³, effortless³, colloquial⁴, nonchalant³, fortuitous⁴, insouciant³
11 letters: superficial⁴, indifferent³, promiscuous³, unconcerned³, perfunctory⁴, pococurante
12 letters: adventitious
13 letters: unintentional⁵, serendipitous⁵
14 letters: extemporaneous

The small number after each word is its number of syllables (easy² = 2 syllables).