Does Tufts count as a liberal arts college?
What I have looked at so far: Wesleyan, Vassar, Bowdoin, Middlebury, Trinity…
But wondering what the largest known LAC is in terms of undergraduate enrollment
I would say Bucknell is at 3600 enrollment. Holy Cross, Colgate and Wesleyan are a bit larger than normal too.
Why does it matter so much?
Tufts is not an LAC.
Also a LAC is generally an undergraduate only or a primarily undergraduate institution. A bit more than half of Tufts student body is made up of grad students. https://www.tufts.edu/about/tufts-at-a-glance
It is more important to find schools that match what you want in a college than to worry about labels like if the school is a LAC or not.
Notre Dame at 8,500 undergraduate about 75% of total enrollment is more like an LAC than Tufts, plus the residential system makes the school feel much smaller.
^^^^My H and S went to ND and my D recently graduated from a LAC. While there is a large undergraduate population by percentage at ND, from everything I have seen firsthand and heard from my kids, the size of the school and campus (not to mention the huge sports scene) make the ND experience very different from an LAC experience. One is not better or worse than the other, but IMO they are different. If others have first-hand knowledge of both ND and LACs and see it differently then we will have to agree to disagree.
The term “LAC” has different connotations these days. Many large state public flagship universities refer to their honors colleges as “LAC” or “LAC” equivalent. Long established LAC privates with a pre-professional program (for example teaching externships), and engineering or business studies don’t fit the traditional definition of LAC anymore but in many cases you would need to comb through the course catalogs to figure that out. I think there is a good case for regarding the 5-college Claremonts together as a large LAC.
ND isn’t all things to all people… it is NOT a LAC, nor does it really feel like one.
The five Claremonts really are all LACs, with the benefit of sharing resources across them. Best of all worlds, in my opinion (but I might be biased because I have a kid at one of them). 
^^ You could view the Haverford/Swarthmore/Bryn Mawr/etc. consortium the same.
Yes, although the 5Cs are the most tightly integrated consortium in the country – my kid can seamlessly register and attend classes back to back across them without worrying about transit time, etc (she does hop on her scooter or longboard to go to Pomona, but it is less than 5 minutes).
Last time I checked ND did not have a medical, dental or veterinary school and last time I checked there was a pretty heavy arts and sciences core curriculum. 14 courses maybe. And the rule is professors must teach. Somewhere also there is a quote from Hesburgh saying something like this “Notre Dame is first and foremost an undergraduate institution and will remain that way”. Oh yes when I graduated in 1986 I recall that.
Another idea for the OP is Dartmouth.
“more like”
My D’s LAC (Lafayette College) was also in a consortium which included Lehigh, Muhlenberg and a couple of other nearby schools. My D and many of her friends were able to take a class not offered at Lafayette at these schools. In addition, the consortium also coordinated on providing a nice array of summer abroad programs.
(and PS…I don’t’ think ND is anything like a LAC despite the focus on the undergraduate student)
Largest LACs, by Campus Acreage
- Berry
- Sewanee
- Sweet Briar
- Principia
- Saint John's (MN)
- Hamilton
- Hampden-Sydney
- Houghton
- Kenyon
- Warren Wilson
The little chicks might pay attention to what constitutes a LAC. ND isn’t an LAC, it has grad students, TAs (there are almost as many teaching grad students as tenured faculty), DI sports (and athletic scholarships), and over 10,000 students. They have colleges of engineering, business, and architecture. They are NOT a LAC.
And in their own words, Notre Dame via their website, describes the school as a research university
Tufts is not officially an LAC but definitely has the vibe, especially considering several of the graduate departments are off the Somerville/Medford campus.
*Closing thread. If the OP wants to specify whether they mean the more strict definition of LAC (minimal grad students, not a research university, at one time known as a college as opposed to a university) or broaden it to schools that people want to argue feel like an LAC even though they award Ph.D. degrees in more than a few fields, then it can be reopened. I assume they mean the former, in which case Tufts and ND are NOT LACs. But until they contact me via PM to say, there will just be too much bickering to make the thread viable.
In any case, @OnTheBubble, with respect to posts 3 and 9 the OP didn’t ask for “more like”, they asked about LACs themselves, and there is indeed a fairly traditional definition.*