Drugs
Medicine
noun
These medicine things are of the bad kind, they're drugs!
As a standalone word, 薬物 generally refers to (often) illegal drugs that cause addiction or have a stimulating effect. Depending on the context, it can also refer to pharmaceutical drugs (aka medicine), but in that case, it's usually used in compounds like 薬物アレルギー (drug allergy).
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
今すぐ薬物をやめろ！
Stop doing drugs right now!
あのヤクザは薬物取引をしているそうだ。
I heard that those yakuza are doing drug deals.
どうやらあの薬物使用者には幻覚が見えているらしい。
Apparently, that drug user is having hallucinations.