First of all, a correction:
The Modern Hebrew word for jet lag - יַעֶפֶת (yah-EH-fet) comes from the root י.ע.פ (y.a'.f), meaning flight. It doesn't come from the acrobatic linguistic act I described the other day. Thanks for the tip, Larry.
Now for today's dose...
The proper way of saying save me a spot is, to a male, שָׁמוֹר לִי מָקוֹם (shah-MOHR lee mah-KOHM), though the first word is pronounced by most speakers, שְׁמוֹר (shmohr).
However, today many speakers are likely to use a colloquialism, borrowing the word to safeguard or to ensure - לְשַׁרְיֵן (leh-shahr-YEN). They might say to a male, שַׁרְיֵן אֶת הַשְּׁלִישִּׁי לַחוֹדֶשׁ, אֲנַחְנוּ עוֹשִׂים מְסִבָּה (shahr-YEN et hah-shlee-SHEE lah-KHOH-desh, ah-NAHKH-noo oh-SEEM meh-see-BAH) - Set aside the third of the month, we're making a party.
לשריין comes from the word שִׁרְיוֹן (sheer-YOHN), meaning armor. It's also in the name of the tanks unit of the IDF - חֵיל הַשִּׁרְיוֹן (kheil hah-sheer-YOHN).
לשריין falls into the active-intensive פיעל (pee-EL) verb form.