opportunistic

American  

[op-er-too-nis-tik, -tyoo-] / ˌɒp ər tuˈnɪs tɪk, -tyu- /

adjective

1. adhering to a policy of opportunism; practicing opportunism.

2. Pathology.

   1. (of a microorganism) causing disease only under certain conditions, as when a person's immune system is impaired.

   2. (of a disease or infection) caused by such an organism.

      Pneumocystis pneumonia is an opportunistic disease that often strikes victims of AIDS.

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opportunistic British  

/ ˌɒpətjʊˈnɪstɪk /

adjective

1. of or characterized by opportunism

2. med (of an infection) caused by any microorganism that is harmless to a healthy person but debilitates a person whose immune system has been weakened by disease or drug treatment

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Other Word Forms

• opportunistically adverb
• unopportunistic adjective

Etymology

Origin of opportunistic

First recorded in 1890–95; opportunist + -ic

Explanation

To be opportunistic is to quickly take advantage of a situation, usually in a way that's just plain wrong. You know how an opportunity is a chance to do something? When you're opportunistic, you take advantage of that chance, usually immediately. Most of the time, this word is not neutral: people described as opportunistic are also considered unethical, like a business taking advantage of employees or customers in an opportunistic way. If someone dropped their wallet and someone else found it and kept it, that would be opportunistic. Being opportunistic is shady and self-serving.

Example Sentences

A pirate attack off Somalia is the work of a new group of "opportunistic criminals", security officials said on Tuesday, complicating a threat that costs the shipping industry billions of dollars.

From Barron's • Apr. 28, 2026

To investigate, researchers built a catalog of individual whales using opportunistic sightings and photographs contributed by the public between 2018 and 2023, along with more structured surveys conducted from 2023 to 2025.

From Science Daily • Apr. 13, 2026

An "opportunistic" thief who stole a handbag containing an emerald-encrusted Fabergé egg and watch set worth up to £2.2 million from a central London pub has been jailed for more than two years.

From BBC • Apr. 9, 2026

“It speaks to the opportunistic behavior of everyone involved—it could be opportunistic set months earlier, it could be opportunistic in the moment,” said Ben Silverman, head of research at VerityData.

From The Wall Street Journal • Apr. 8, 2026

Imagine that O’Connor had written Herons are opportunistic hunters, but great blues defend a fishing hole even when it’s frozen.

From "The Sense of Style" by Steven Pinker

Related Words

• cosmopolitan
• hardened
• practical
• selfish
• urbane