semisynthetic
adjective
semi·syn·thet·ic
ˌse-mē-sin-ˈthe-tik 
ˌse-ˌmī-,
-mi-
1
: produced by chemical alteration of a natural starting material
semisynthetic penicillins
2
: containing both chemically identified and complex natural ingredients
a semisynthetic diet
3
: partly synthetic
semisynthetic motor oil
Examples of semisynthetic in a Sentence
Recent Examples on the Web
The type of oil – synthetic, semisynthetic/blended or conventional − is also key, with full synthetic oils generally promising more miles between changes.
—
Eric D. Lawrence, USA Today, 7 Oct. 2025
The Botanic Tonics representative maintained that its kratom products are safe compared with semisynthetic 7-OH.
—Kristen Rogers, CNN Money, 26 Aug. 2025
There were also some declines seen in certain drugs, with lower rates reported for heroin, natural and semisynthetic opioids, and methadone.
—CBS News, 22 Mar. 2024
Between 2021 and 2022, the death rate involving synthetic opioids other than methadone -- such as fentanyl -- increased by 4.1% from 21.8 per 100,000 to 22.7 per 100,000, while rates for deaths involving heroin, natural and semisynthetic opioids and methadone declined.
—Mary Kekatos, ABC News, 20 Mar. 2024
The rate of drug overdose deaths involving heroin, natural and semisynthetic opioids and methadone were lower in 2018 than the previous year.
—Janet Adamy, WSJ, 30 Jan. 2020
Hydrocodone and oxycodone are semisynthetic opioids used to treat pain.
—Author: Lindsey Bever, Anchorage Daily News, 1 Feb. 2018
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Eric D. Lawrence, USA Today, 7 Oct. 2025
The Botanic Tonics representative maintained that its kratom products are safe compared with semisynthetic 7-OH.
—Kristen Rogers, CNN Money, 26 Aug. 2025
There were also some declines seen in certain drugs, with lower rates reported for heroin, natural and semisynthetic opioids, and methadone.
—CBS News, 22 Mar. 2024
Between 2021 and 2022, the death rate involving synthetic opioids other than methadone -- such as fentanyl -- increased by 4.1% from 21.8 per 100,000 to 22.7 per 100,000, while rates for deaths involving heroin, natural and semisynthetic opioids and methadone declined.
—Mary Kekatos, ABC News, 20 Mar. 2024
The rate of drug overdose deaths involving heroin, natural and semisynthetic opioids and methadone were lower in 2018 than the previous year.
—Janet Adamy, WSJ, 30 Jan. 2020
Hydrocodone and oxycodone are semisynthetic opioids used to treat pain.
—Author: Lindsey Bever, Anchorage Daily News, 1 Feb. 2018
Cite this Entry
“Semisynthetic.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/semisynthetic. Accessed 31 Oct. 2025.
Copy CitationMedical Definition
semisynthetic
adjective
semi·syn·thet·ic
-sin-ˈthet-ik
1
: produced by chemical alteration of a natural starting material
semisynthetic penicillins
2
: containing both chemically identified and complex natural ingredients
a semisynthetic diet
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