맙시다 is composed of 말(다) + -(으)ㅂ시다 말다 means "stop doing ..." Quoted from http://www.livingincmajor.com/my-korean-grammar-usage-note-5-lets We use -(으)ㅂ시다 to express a suggestion or proposition; to express agreement with or acceptance of another’s suggestion. 01 Let’s… Verb + (으)ㅂ시다 If the verb stem ends with a vowel (no batchim), -ㅂ시다 is added. If the verb stem ends with a consonant (with batchim), -읍시다 is added. 가다 (to go) → 갑시다 자다 (to sleep) → 잡시다 마시다 (to drink) → 마십시다 쇼핑하다 (to shop) → 쇼핑합시다 읽다 (to read) → 읽읍시다 먹다 (to eat) → 먹읍시다 02 Irregular Forms Irregular form ‘ㄷ’ 듣다 (to listen) → 들읍시다 걷다 (to walk) → 걸읍시다 묻다 (to ask) → 물읍시다 닫다 (to close) → 닫읍시다 받다 (to receive) → 받읍시다 Irregular form ‘ㄹ’ 알다 (to know) → 압시다 살다 (to live) → 삽시다 놀다 (to play) → 놉시다 03 Let’s not… Verb + 지 맙시다 The negative form is -지 맙시다. It is added directly to the verb stem, regardless of whether the verb stem ends in a vowel or a consonant (with/without batchim). 수영하다 (to swim) → 수영하지 맙시다 듣다 (to listen) → 듣지 맙시다 보다 (to watch) → 보지 맙시다 나가다 (to go out) → 나가지 맙시다 놀다 (to play) → 놀지 맙시다 쓰다 (to write) → 쓰지 맙시다