noun
cheap SIM card; budget SIM
Typically refers to a low-cost SIM card provided by an MVNO (mobile virtual network operator) in Japan, as opposed to a major carrier's SIM.
格安ＳＩＭに乗り換えて、毎月の通信費を半分にした。
I switched to a cheap SIM card and cut my monthly communication costs in half.
格安ＳＩＭは大手キャリアよりずっと安い。
Cheap SIM cards are much cheaper than those from major carriers.
General term for a SIM card; 格安ＳＩＭ specifically emphasizes low cost and is often associated with MVNOs.
Mobile virtual network operator; the type of company that typically offers 格安ＳＩＭ services.
Compound of 格安 (かくやす, 'bargain-priced') and ＳＩＭ (シム, 'SIM card'). The term became common in Japan with the rise of MVNOs offering low-cost mobile plans.