To be intrusive is to involve oneself into the affairs of others, generally in an objectionable manner, tactlessly but not necessarily in a way that calls attention to oneself. To be obtrusive, by contrast, is to interfere without regard for propriety or subtlety. They therefore can apply to the same situation, but intrusive emphasizes the effect on the recipient of the attention, while obtrusive focuses how the attention is perceived from the outside.

The common element in intrude and obtrude, the root words for these synonyms, is -trude, from the Latin word trudere, which means “to thrust.” Ob- means “toward,” and in- is self-explanatory; protrusive, from protrude, featuring a prefix meaning “forward,” also means “pushy” but is used less often in this context. (Yet another word featuring the stem is extrude, which means “to thrust out”; the adjectival form is extrusive.)

Other synonyms for this behavior follow:

Impertinent: insolent or unrestrained, though it also has an unrelated original sense of irrelevance (from the Latin word pertinere, meaning “to pertain”)

Insinuating: stealthily ingratiating, though the more common definition is “to imply or covertly suggest” (from the Latin word sinuare, also the origin of sinuous and meaning “to bend, curve”)

Meddlesome or meddling: interfering (from the Latin word miscere, meaning “to mix”)

Officious: interfering (from the Latin word officium, meaning “service, office”)

Presumptuous or presuming: going beyond the bounds of what is considered appropriate (from the Latin word praesumere, meaning “to anticipate, assume, or dare”)

Informal and slang terms for intrusive or obtrusive behavior include nosy (also spelled nosey), prying, pushy, and snoopy. Related descriptive phrases include “being a busybody” and “butting in.”