catch someone's drift (or get someone's drift)
informal phrase

- to understand in a general way what someone is telling you

(Cambridge Dictionary)

---
ORIGIN

Although the expression "catch someone's drift" became popular only over the last 50 or so years, the word drift, as in the general meaning of speech or writing, goes back to the 16th century.

Drift has its roots in the word "drive," which has developed numerous meanings and contexts since it first started to appear in Old English (13th century).

These meanings range from literally moving something with force (They drove the cattle across the range for two weeks) to the more figurative sense of making something happen through one's own will (He drives a really hard bargain).

Another figurative use, which goes back to the 16th century, refers to "proceeding with a definite intention; to mean or intend." It's this sense of drive that makes up the underlying substance of drift.

It's important to note that "catch my drift" is an informal expression. In a casual conversation with friends or co-workers, it's okay to say "I catch your drift" as a way to explain that you understand what someone means or is trying to tell you.

It can also be used in place of the expression "If you know what I mean," to indicate that someone should be able to understand the hidden meaning behind what you just said (He's married, but seems to act a bit too friendly with females in the office,... if you catch my drift).

This expression is not appropriate in formal business situations however. If a superior explains something, which you want to indicate that you understand, don't use "I catch your drift." Better to simply say "I understand" or "That's clear".

---
SYNONYMS

I get the idea, I get the picture, I see what you're getting at

---
SMUGGLE OWAD into a conversation, say something like:

"That was a complicated explanation, but I think I CATCH YOUR DRIFT."