How do you say get lost in welsh?

There isn't a direct equivalent to "get lost" in Welsh that conveys the same sense of annoyance or dismissal. It's best to use a phrase that expresses the desired meaning depending on the context:

For someone being annoying:

* "Dos i ffwrdd!" (Go away!) - This is the most direct and rude way to say it.

* "Gad i mi'n dawel!" (Leave me alone!) - A more assertive way to ask someone to leave.

* "Dwi'n dy foddi di!" (I'm sick of you!) - This is a more informal and playful way to say "get lost," suggesting annoyance.

For someone being in the way:

* "Symud o'r ffordd!" (Move out of the way!) - This is direct and practical.

* "Does dim lle yma i ti!" (There's no room here for you!) - This conveys a sense of being crowded.

For someone being unwanted:

* "Fydda i ddim eisiau dy weld eto!" (I don't want to see you again!) - This is a strong way to tell someone to leave.

* "Nid oes gen i ddiddordeb!" (I'm not interested!) - This conveys disinterest and a desire to be left alone.

Remember, the best way to say "get lost" in Welsh depends on the situation and your desired tone.