informal

Not formal or ceremonious.

an informal get-together

One saint's day in mid-term a certain newly appointed suffragan-bishop came to the school chapel, and there preached on “The Inner Life.” He at once secured attention by his informal method, and when presently the coughing of Jarvis […] interrupted the sermon, he altogether captivated his audience with a remark about cough lozenges being cheap and easily procurable.

Not in accord with the usual regulations.

an informal agreement

Suited for everyday use.

informal clothes

Reflecting everyday, non-ceremonious usage.

When I returned to the movie Ghilli, a Kollywood classic (Kollywood being the informal name for Tamil cinema) that I loved as a kid, I couldn’t help but question why the story continues romantically, without question, after the heroine is slapped by the supposed love of her life.

Not organized; not structured or planned.