Sending a tiny or zero-value transfer from an address whose first and last characters match one you have used, so that copying from your transaction history yields the attacker’s address.
Why it matters
It exploits the habit of verifying an address by its ends rather than in full, and the habit of copying from history rather than from source. The defence is checking the entire address on the signing device, every time it matters.
What you can check
Compare the full string, not the ends. Block explorers show the complete address, and most wallets let you label an address once you have verified it, so later transfers reference a name you set rather than a string you re-read. A zero-value or dust-sized incoming transfer from a near-identical address is the signature of the technique.
Not advice. Definitions are for understanding, not instruction. Nothing here is financial, legal, tax or security advice.